Instead of always reporting some object cannot be implicitly be converted
to a 'str', even when it is a 'bytes' object, adjust the logic so that
when trying to convert str to bytes it is shown like that.
This will still report bad implicit conversion from e.g. 'int to bytes'
as 'int to str' but it will not result in the confusing
'can't convert 'str' object to str implicitly' anymore for calls like
b'somestring'.count('a').

* Fix mis-spelling of `ticks_add` in code examples.
* Be consistent about parentheses after function names.
* Be consistent about formatting of function, variable and constant names.
* Be consistent about spaces and punctuation.
* Fix some language errors (missing or wrong words, wrong word order).
* Keep line length under 90 chars.

Signed-off-by: Christopher Arndt <chris@chrisarndt.de>

This has a noticeable improvement on x86-64 and Thumb2 archs, where stack
usage is reduced by 2 machine words in the VM.

Instead of caching data that is constant (code_info, const_table and
n_state), store just a pointer to the underlying function object from which
this data can be derived.

This helps reduce stack usage for the case when the mp_code_state_t
structure is stored on the stack, as well as heap usage when it's stored
on the heap.

The downside is that the VM becomes a little more complex because it now
needs to derive the data from the underlying function object.  But this
doesn't impact the performance by much (if at all) because most of the
decoding of data is done outside the main opcode loop.  Measurements using
pystone show that little to no performance is lost.

This patch also fixes a nasty bug whereby the bytecode can be reclaimed by
the GC during execution.  With this patch there is always a pointer to the
function object held by the VM during execution, since it's stored in the
mp_code_state_t structure.

The RHS can only be returned if it is the same type as the LHS.

This allows to test the PYBV11 target as well as the network drivers
without adding another rule.  It also removes the need to use -B,
side-stepping the issue of whether or not -B works with qstr auto
generation.

When make is passed "-B" it seems that everything is considered out-of-date
and so $? expands to all prerequisites.  Thus there is no need for a
special check to see if $? is emtpy.

Assertions are used to check expressions that should always be true,
and mp_not_implemented is used for code that can be reached.

This is so the test can run successfully on targets that already have
something mounted.

The 'S' typecode is a uPy extension so it should be grouped with the other
extension (namely 'O' typecode).  Testing 'S' needs uctypes which is an
extmod module and not always available, so this test is made optional and
will only be run on ports that have (u)struct and uctypes.  Otherwise it
will be silently skipped.

Some stack is allocated to format ints, and when the int implementation uses
long-long there should be additional stack allocated compared with the other
cases.  This patch uses the existing "fmt_int_t" type to determine the
amount of stack to allocate.

The lexer constructor may now raise an exception and it needs to be caught.

And raise an exception when mp_lexer_new_from_file is called.

And raise an exception when mp_lexer_new_from_file is called.

And raise an exception when mp_lexer_new_from_file is called.

And raise an exception when mp_lexer_new_from_file is called.

The lexer can now raise an exception on construction so it must go within
an nlr handler block.

The lexer can now raise an exception on construction so it must go within
an nlr handler block.

This patch refactors the error handling in the lexer, to simplify it (ie
reduce code size).

A long time ago, when the lexer/parser/compiler were first written, the
lexer and parser were designed so they didn't use exceptions (ie nlr) to
report errors but rather returned an error code.  Over time that has
gradually changed, the parser in particular has more and more ways of
raising exceptions.  Also, the lexer never really handled all errors without
raising, eg there were some memory errors which could raise an exception
(and in these rare cases one would get a fatal nlr-not-handled fault).

This patch accepts the fact that the lexer can raise exceptions in some
cases and allows it to raise exceptions to handle all its errors, which are
for the most part just out-of-memory errors during construction of the
lexer.  This makes the lexer a bit simpler, and also the persistent code
stuff is simplified.

What this means for users of the lexer is that calls to it must be wrapped
in a nlr handler.  But all uses of the lexer already have such an nlr
handler for the parser (and compiler) so that doesn't put any extra burden
on the callers.