With this patch the n_args parameter is changed type from mp_uint_t to
size_t.

This patch changes the type signature of .make_new and .call object method
slots to use size_t for n_args and n_kw (was mp_uint_t.  Makes code more
efficient when mp_uint_t is larger than a machine word.  Doesn't affect
ports when size_t and mp_uint_t have the same size.

Only types whose iterator instances still fit in 4 machine words have
been changed to use the polymorphic iterator.

Reduces Thumb2 arch code size by 264 bytes.

This allows the mp_obj_t type to be configured to something other than a
pointer-sized primitive type.

This patch also includes additional changes to allow the code to compile
when sizeof(mp_uint_t) != sizeof(void*), such as using size_t instead of
mp_uint_t, and various casts.

Previous to this patch the printing mechanism was a bit of a tangled
mess.  This patch attempts to consolidate printing into one interface.

All (non-debug) printing now uses the mp_print* family of functions,
mainly mp_printf.  All these functions take an mp_print_t structure as
their first argument, and this structure defines the printing backend
through the "print_strn" function of said structure.

Printing from the uPy core can reach the platform-defined print code via
two paths: either through mp_sys_stdout_obj (defined pert port) in
conjunction with mp_stream_write; or through the mp_plat_print structure
which uses the MP_PLAT_PRINT_STRN macro to define how string are printed
on the platform.  The former is only used when MICROPY_PY_IO is defined.

With this new scheme printing is generally more efficient (less layers
to go through, less arguments to pass), and, given an mp_print_t*
structure, one can call mp_print_str for efficiency instead of
mp_printf("%s", ...).  Code size is also reduced by around 200 bytes on
Thumb2 archs.

mp_obj_t internal representation doesn't have to be a pointer to object,
it can be anything.

There's also a support for back-conversion in the form of MP_OBJ_UNCAST.
This is kind of optimization/status quo preserver to minimize patching the
existing code and avoid doing potentially expensive MP_OBJ_CAST over and
over. But then one may imagine implementations where MP_OBJ_UNCAST is very
expensive. But such implementations are unlikely interesting in practice.

This is rarely used feature which takes enough code to implement, so is
controlled by MICROPY_PY_ARRAY_SLICE_ASSIGN config setting, default off.
But otherwise it may be useful, as allows to update arbitrary-sized data
buffers in-place.

Slice is yet to implement, and actually, slice assignment implemented in
such a way that RHS of assignment should be array of the exact same item
typecode as LHS. CPython has it more relaxed, where RHS can be any sequence
of compatible types (e.g. it's possible to assign list of int's to a
bytearray slice).

Overall, when all "slice write" features are implemented, it may cost ~1KB
of code.

This makes exception traceback info self contained (ie doesn't rely on
list object, which was a bit of a hack), reduces code size, and reduces
RAM footprint of exception by eliminating the list object.

Addresses part of issue #1126.

Traceback allocation for exception will now never lead to recursive
MemoryError exception - if there's no memory for traceback, it simply
won't be created.

Also fix list.sort so it works with user-defined types, and parse the
keyword arguments properly.

Addresses issue #338.

See issue #699.

See issue #699.

Addresses issue #1022.

Addressing issue #50.

Also add start of ujson module with dumps implemented.  Enabled in unix
and stmhal ports.  Test passes on both.

Part of code cleanup, to resolve issue #50.

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

Found this bug by running unix/ tests with DEBUG=1 enabled when
compiling.

Multiplication of a tuple, list, str or bytes now yields an empty
sequence (instead of crashing).  Addresses issue #799

Also added ability to mult bytes on LHS by integer.

See discussion in issue #50.

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.

This means that complete slice operations are supported for lists (but not
for bytearray's and array.array's).

Now of the form MICROPY_PY_*.  See issue #35.

See issue #608 for justification.

Updated functions now do proper checking that n_kw==0, and are simpler
because they don't have to explicitly raise an exception.  Down side is
that the error messages no longer include the function name, but that's
acceptable.

Saves order 300 text bytes on x64 and ARM.

Slice value to assign can be only a list so far too.

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/.

Specifically, nlr.h does.

Also, clear up freed slots in containers.

As a follow up to 32bef315.