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.

Hashing is now done using mp_unary_op function with MP_UNARY_OP_HASH as
the operator argument.  Hashing for int, str and bytes still go via
fast-path in mp_unary_op since they are the most common objects which
need to be hashed.

This lead to quite a bit of code cleanup, and should be more efficient
if anything.  It saves 176 bytes code space on Thumb2, and 360 bytes on
x86.

The only loss is that the error message "unhashable type" is now the
more generic "unsupported type for __hash__".

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.

This is so all memory requests go through the same interface.

See issue #699.

Addresses issue #1022.

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.

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.

Some small fixed:

- Combine 'x' and 'X' cases in str format code.

- Remove trailing spaces from some lines.

- Make exception messages consistently begin with lower case (then
needed to change those in objarray and objtuple so the same
constant string data could be used).

- Fix bug with exception message having %c instead of %%c.

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.

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.

Likely there are other functions that should be renamed, but this is a
start.

Two things are handled here: allow to compare native subtypes of tuple,
e.g. namedtuple (TODO: should compare type too, currently compared
duck-typedly by content). Secondly, allow user sunclasses of tuples
(and its subtypes) be compared either. "Magic" I did previously in
objtype.c covers only one argument (lhs is many), so we're in trouble
when lhs is native type - there's no other option besides handling
rhs in special manner. Fortunately, this patch outlines approach with
fast path for native types.

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 make consistent use of MP_OBJ_NOT_SUPPORTED and MP_OBJ_NULL.
This helps a lot in debugging and understanding of function API.

mp_obj_t->subscr now does load/store/delete.

I'm pretty sure these are never reached, since NOT_EQUAL is always
converted into EQUAL in mp_binary_op.  No one should call
type.binary_op directly, they should always go through mp_binary_op
(or mp_obj_is_equal).

This does not affect code size or performance when debugging turned off.

To address issue #420.

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.

Mostly just a global search and replace.  Except rt_is_true which
becomes mp_obj_is_true.

Still would like to tidy up some of the names, but this will do for now.

Addresses issue #388.