created SDdatalogger example
deleted garbage
py: Turn down amount of RAM parser and compiler use.

There are 2 locations in parser, and 1 in compiler, where memory
allocation is not precise.  In the parser it's the rule stack and result
stack, in the compiler it's the array for the identifiers in the current
scope.  All other mallocs are exact (ie they don't allocate more than is
needed).

This patch adds tuning options (MP_ALLOC_*) to mpconfig.h for these 3
inexact allocations.

The inexact allocations in the parser should actually be close to
logarithmic: you need an exponentially larger script (absent pathological
cases) to use up more room on the rule and result stacks.  As such, the
default allocation policy for these is now to start with a modest sized
stack, but grow only in small increments.

For the identifier arrays in the compiler, these now start out quite
small (4 entries, since most functions don't have that many ids), and
grow incrementally by 6 (since if you have more ids than 4, you probably
have quite a few more, but it wouldn't be exponentially more).

Partially addresses issue #560.
Merge pull request #566 from turbinenreiter/master

added SDdatalogger example
examples, SDdatalogger: Add more comments; reduce power consumption.
Change references (in comments) of pyb.GPIO to be pyb.Pin

The documentation at http://micropython.org/doc/module/pyb/ExtInt should also be
updated.
Merge pull request #571 from dhylands/fix-extint-doc

Change references (in comments) of pyb.GPIO to be pyb.Pin
py-version.sh: Use --always option of git describe.
py: Comment exc_state member from mp_obj_gen_instance_t as it gives trouble

...to some compilers who can't process 2 zero-sized arrays in structs. It's
never referenced directly anyway.

See disussion on #568 as well.
modgc: Add new module for GC-related functionality.
stmhal: pyb: Use gc() function as defined by standard module "gc".

TODO: Get rid of this compatibility define and rely on standard module.
Windows MSVC port

Extend the windows port so it compiles with the toolchain from Visual Studio 2013