At this point, all opcodes are now implemented!

Some del opcodes have been combined with store opcodes, with the value
to store being MP_OBJ_NULL.

To create bytearray of given length.

If no nlr_buf has been pushed, and an nlr_jump is called, then control
is transferred to nlr_jump_fail (which should bail out with a fatal
error).

To keep it maintainable, windows port now uses as much as possible from
unix port.  Maybe could even use mpconfigport.h.

Display \r and \t escape codes in string repr

Full CPython compatibility with this requires actually parsing the
input so far collected, and if it fails parsing due to lack of tokens,
then continue collecting input.  It's not worth doing it this way.  Not
having compatibility at this level does not hurt the goals of Micro
Python.

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.