Found these by compiling stmhal with mp_uint_t of type uint32_t instead
of unsigned int.  This actually makes a difference to the code, but just
a curiosity.

Addressing issue #50, still some way to go yet.

Also added test for modtime.

Now you can use time.localtime on the timestamps presented by os.stat

This renames:
MICROPY_PY_FROZENSET -> MICROPY_PY_BUILTINS_FROZENSET
MICROPY_PY_PROPERTY -> MICROPY_PY_BUILTINS_PROPERTY
MICROPY_PY_SLICE -> MICROPY_PY_BUILTINS_SLICE
MICROPY_ENABLE_FLOAT -> MICROPY_PY_BUILTINS_FLOAT

See issue #35 for discussion.

time.time: returns seconds since 1/1/2000, as an integer.

time.localtime: Returns 8-tuple: (year, month, date, hour, minute,
    second, weekday, yearday).

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/.

Towards addressing issue #424.

Had a small increase to ROM usage (order 60 bytes).

Pretty much everyone needs to include map.h, since it's such an integral
part of the Micro Python object implementation.  Thus, the definitions
are now in obj.h instead.  map.h is removed.

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