reversed function now implemented, and works for tuple, list, str, bytes
and user objects with __len__ and __getitem__.

Renamed mp_builtin_len to mp_obj_len to make it publically available (eg
for reversed).

And not system printf(), like it was before. For this, move pfenv_printf()
from stmhal port to py/.

But much smaller and memory-efficient. Uses Python builtin data structures
(dict, tuple, int) to describe structure layout.

.makefile() should allow to specify which stream time to create - byte
or text.

Blanket wide to all .c and .h files.  Some files originating from ST are
difficult to deal with (license wise) so it was left out of those.

Also merged modpyb.h, modos.h, modstm.h and modtime.h in stmhal/.

Addresses issue #487.

Not all functions implemented.  Not enabled on pyboard.

A one-liner, added especially for @pfalcon :)

Only calcsize() and unpack() functions provided so far, for little-endian
byte order. Format strings don't support repition spec (like "2b3i").

Unfortunately, dealing with all the various binary type sizes and alignments
will lead to quite a bloated "binary" helper functions  - if optimizing for
speed. Need to think if using dynamic parametrized algos makes more sense.

That's how CPython has it, in particular, "import __main__" should work.

So far just includes "open" function, which should be supplied by a port.

TODO: Make the module #ifdef'ed.

Comes with some refactoring of code and renaming of files.  All modules
are now named mod*.[ch].

mp_module_obj_t can now be put in ROM.

Configuration of float type is now similar to longint: can now choose
none, float or double as the implementation.

math module has basic math functions.  For STM port, these are not yet
implemented (they are just stub functions).

Only works on modules and class instances.

Currently, MicroPython strings are mix between CPython byte and unicode
strings. So, conversion is null so far. This dummy implementation is
intended for compatibility with CPython (so, same code can run on both).

These are micropython.mem_total(), .mem_current(), .mem_peak(). These are 3
individual functions with simple scalar return value to make sure that
calls to these functions themselves have minimal (hopefully zero) impact on
memory allocation.