This saves 4 words of stack space per Python call.

Add keyword args to dict.update(), and ability to take a dictionary as
argument.

dict() class constructor can now use dict.update() directly.

This patch loses fast path for dict(other_dict), but is that really
needed?  Any anyway, this idiom will now re-hash the dictionary, so is
arguably more memory efficient.

Addresses issue #647.

Support multiple bytecode optimisation levels

To clearly signify that lineno is not known.

This allows to have multiple "optimization" levels (CPython has two
(-OO removes docstrings), we can have more).

Add missing commas to stm32f4xx-af.csv

Also, dump code block in bytes.

Also, add comment with description of extension to CPython's typecodes.

This way, it's slightly more efficient, uses less ROM (60 bytes less
for stmhal), and doesn't require to raise exception if bad operation
given.

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 may seem a bit of a risky change, in that it may introduce crazy
bugs with respect to volatile variables in the VM loop.  But, I think it
should be fine: code_state points to some external memory, so the
compiler should always read/write to that memory when accessing the
ip/sp variables (ie not put them in registers).

Anyway, it passes all tests and improves on all efficiency fronts: about
2-4% faster (64-bit unix), 16 bytes less stack space per call (64-bit
unix) and slightly less executable size (unix and stmhal).

The reason it's more efficient is save_ip and save_sp were volatile
variables, so were anyway stored on the stack (in memory, not regs).
Thus converting them to code_state->{ip, sp} doesn't cost an extra
memory dereference (except maybe to get code_state, but that can be put
in a register and then made more efficient for other uses of it).

Conflicts:
	py/vm.c

Fixed stack underflow check.  Use UINT_FMT/INT_FMT where necessary.
Specify maximum VM-stack byte size by multiple of machine word size, so
that on 64 bit machines it has same functionality as 32 bit.

Add a comma to make the .csv look proper in github

tests: Add argument to allow specifying which directories to test

This improves stack usage in callers to mp_execute_bytecode2, and is step
forward towards unifying execution interface for function and generators
(which is important because generators don't even support full forms
of arguments passing (keywords, etc.)).

This makes sure that only as much stack allocated as actually used, reducing
stack usage for each Python function call.