They correspond to io.FileIO in io module hierarchy (with small caveat
that io.FileIO is raw file and works with bytes, not strings).

stmhal relies on pfenv_* to implement its printf.  Thus, it needs a
pfenv_print_int which prints a proper 32-bit integer.  With latest
change to pfenv, this function became one that took mp_obj_t, and
extracted the integer value from that object.

To fix temporarily, pfenv_print_int has been renamed to
pfenv_print_mp_int (to indicate it takes a mp_obj_t for the int), and
pfenv_print_int has been added (which takes a normal C int).  Currently,
pfenv_print_int proxies to pfenv_print_mp_int, but this means it looses
the MSB.  Need to find a way to fix this, but the only way I can think
of will duplicate lots of code.

Add string formatting support for longlong and mpz.

Partly addresses issue #154.

Makefile tweaks

Modify set tests to print sorted sets directly

Add tests for sorted() function

instead of creating temporary lists and sorting those in-place

and check that sorted(list) produces same output as list.sort()

No longer needed after recent change which guarantees that mp_set_init()
will allocate exact number of slots requested.

Seems that this fixes all set tests.

So, pip-micropython can/should be run as normal pip:

    pip-micropython install micropython-unittest

With dict being unordered of course.

Sure, it's O(n^2).

Two things: 1) set flags in copy properly; make mp_map_init() not be too
smart and do something with requested alloc size. Policy of using prime
numbers for alloc size is high-level policy which should be applied at
corresponding high levels. Low-level functions should just do what they're
asked to, because they don't have enough context to be smarter than that.
For example, munging with alloc size of course breaks dict copying (as
changing sizes requires rehashing).

On x64, native emitter now passes 70 of the tests.

Also add command line option to unix port to select emitter.

Based on the discussion in #433. mp_load_attr() is critical-path function,
so any extra check will slowdown any script. As supporting default val
required only for getattr() builtin, move correspending implementation
there (still as a separate function due to concerns of maintainability
of such almost-duplicated code instances).