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.

add methods isspace(), isalpha(), isdigit(), isupper() and islower() to str

For #635 / 25c84643.

Needed to pop the iterator object when breaking out of a for loop.  Need
also to be careful to unwind exception handler before popping iterator.

Addresses issue #635.

msvc: Only update generated headers when there are changes

Based on https://github.com/micropython/micropython/pull/630 by @errordeveloper.

Needs proper coverage testing.  Doesn't implement -ve & -ve.
Addresses issue #611.

This fixes generating the headers casuing complete rebuilds,
even when the headere's content didn't really change.

Also unifies use of SMALL_INT_FITS macro across parser and runtime.

Addresses issue #627.

This reverts commit 6e76f7bc.

This patch tries to workaround a previous clang workaround. Instead of going
into workaround of workaround spiral, the original workaround should be tamed.

windows: Complete rename of MICROPY_PATH_MAX to MICROPY_ALLOC_PATH_MAX (...