This path for src->deg==NULL is never used because mpz_clone() is always
called with an argument that has a non-zero integer value, and hence has
some digits allocated to it (mpz_clone() is a static function private to
mpz.c all callers of this function first check if the integer value is zero
and if so take a special-case path, bypassing the call to mpz_clone()).

There is some unused and commented-out functions that may actually pass a
zero-valued mpz to mpz_clone(), so some TODOs are added to these function
in case they are needed in the future.

There is a finite list of ascending primes used for the size of a hash
table, and this test tests that the code can handle a dict larger than the
maximum value in that list of primes.  Adding this tests gets py/map.c to
100% coverage.

Adding this test gets py/objtype.c to 100% coverage.

All callers of the asm entry function guarantee that num_locals>=0, so no
need to add an explicit check for it.  Use an assertion instead.

Also, the signature of asm_x86_entry is changed to match the other asm
entry functions.

Makes the flow of the function a little more obvious, and allows to reach
100% coverage of compile.c when using gcov.

It's declared already in py/builtin.h.

This patch just moves the definition of the wrapper object fat_vfs_open_obj
to the location of the definition of its function, which matches how it's
done in most other places in the code base.

The only function left in vfs_fat_misc.c is fat_vfs_import_stat() which
can logically go into vfs_fat.c, allowing to remove vfs_fat_misc.c.

The fat_vfs_ilistdir2() function was only used by fat_vfs_ilistdir_func()
so moving the former into the same file as the latter allows it to be
placed directly into the latter function, thus saving code size.

It's cleaner to have all the MCU-specific configuration in one location,
not least to help with adding support for a new MCU series.

Instead of "Create", to match the build output from the py/ core.

Otherwise the build process puts the corresponding output object files in
two directories lower, not in build/ports/unix.

Some ".." need to be changed to $(MPTOP), and in some places "ports/" needs
to be inserted to get to the "ports/unix/" subdir.

The new option is MICROPY_HW_ENABLE_ADC and is enabled by default.

The bare-metal port needs it and it's no longer included by default since
the Makefile now uses $(PY_CORE_O).

This just makes it a bit cleaner in the output of the build process:
instead of "CC ../../py/../extmod/" there is now "CC ../../extmod/".

These ports don't need anything from extmod so don't include those files
at all in the build.  This speeds up the build by about 10% when building
with a single core.

If a port only needs the core files then it can now use the $(PY_CORE_O)
variable instead of $(PY_O).  $(PY_EXTMOD_O) contains the list of extmod
files (including some files from lib/). $(PY_O) retains its original
definition as the list of all object file (including those for frozen code)
and is a convenience variable for ports that want everything.

Saves a few bytes of code space, and is more efficient because with
MICROPY_GC_CONSERVATIVE_CLEAR enabled by default all memory is already
cleared when allocated.

Otherwise passing -1 as maxlen will lead to a zero allocation and
subsequent unbound buffer overflow in deque.append() because i_put is
allowed to grow without bound.

These ports are all capable of running uasyncio.

So far, implements just append() and popleft() methods, required for
a normal queue. Constructor doesn't accept an arbitarry sequence to
initialize from (am empty deque is always created), so an empty tuple
must be passed as such. Only fixed-size deques are supported, so 2nd
argument (size) is required.

There's also an extension to CPython - if True is passed as 3rd argument,
append(), instead of silently overwriting the oldest item on queue
overflow, will throw IndexError. This behavior is desired in many
cases, where queues should store information reliably, instead of
silently losing some items.

Currently only the first 2 args are used, but this patch should at least
make getaddrinfo() signature-compatible with CPython and other bare-metal
ports that use the lwip bindings.

This allows to get slightly more memory for the heap (currently around 110k
vs previous 92k) because the ESP IDF frees up some RAM after booting up.

This update requires a new ESP32 toolchain: 1.22.0-80-g6c4433a-5.2.0.

At this point in the code the variable "splits" is guaranteed to be
positive due to the check for "splits == 0" above it.

The micropython.stack_use() function is useful to query the current C stack
usage, and it's inclusion in the micropython module doesn't need to be tied
to the inclusion of mem_info()/qstr_info() because it doesn't rely on any
of the code from these functions.  So this patch introduces the config
option MICROPY_PY_MICROPYTHON_STACK_USE which can be used to independently
control the inclusion of stack_use().  By default it is enabled if
MICROPY_PY_MICROPYTHON_MEM_INFO is enabled (thus not changing any of the
existing ports).

The new option is MICROPY_ENABLE_EXTERNAL_IMPORT and is enabled by default
so that the default behaviour is the same as before.  With it disabled
import is only supported for built-in modules, not for external files nor
frozen modules.  This allows to support targets that have no filesystem of
any kind and that only have access to pre-supplied built-in modules
implemented natively.

Prior to this patch uPy (on a 32-bit arch) would have severe issues when
calling bytes(-1): such a call would call vstr_init_len(vstr, -1) which
would then +1 on the len and call vstr_init(vstr, 0), which would then
round this up and allocate a small amount of memory for the vstr.  The
bytes constructor would then attempt to zero out all this memory, thinking
it had allocated 2^32-1 bytes.

This patch changes the way REPL autocomplete finds matches.  It now probes
the target object for all qstrs via mp_load_method_maybe to look for a
match with the given input string.  Similar to how the builtin dir()
function works, this new algorithm now find all methods and instances of
user-defined classes including attributes of their parent classes.  This
helps a lot at the REPL prompt for user-discovery and to autocomplete names
even for classes that are derived.

The downside is that this new algorithm is slower than the previous one,
and in particular will be slower the more qstrs there are in the system.
But because REPL autocomplete is primarily used in an interactive way it is
not that important to make it fast, as long as it is "fast enough" compared
to human reaction.

On a slow microcontroller (CPU running at 16MHz) the autocomplete time for
a list of 35 names in the outer namespace (pressing tab at a bare prompt)
takes about 160ms with this algorithm, compared to about 40ms for the
previous implementation (this time includes the actual printing of the
names as well).  This time of 160ms is very reasonable especially given the
new functionality of listing all the names.

This patch also decreases code size by:

   bare-arm:    +0
minimal x86:  -128
   unix x64:  -128
unix nanbox:  -224
      stm32:   -88
     cc3200:   -80
    esp8266:   -92
      esp32:   -84

This patch improves the builtin dir() function by probing the target object
with all possible qstrs via mp_load_method_maybe.  This is very simple (in
terms of implementation), doesn't require recursion, and allows to list all
methods of user-defined classes (without duplicates) even if they have
multiple inheritance with a common parent.  The downside is that it can be
slow because it has to iterate through all the qstrs in the system, but
the "dir()" function is anyway mostly used for testing frameworks and user
introspection of types, so speed is not considered a priority.

In addition to providing a more complete implementation of dir(), this
patch is simpler than the previous implementation and saves some code
space:

   bare-arm:   -80
minimal x86:   -80
   unix x64:   -56
unix nanbox:   -48
      stm32:   -80
     cc3200:   -80
    esp8266:  -104
      esp32:   -64