This has benefits all round: code factoring for parse/compile/execute,
proper context save/restore for exec, allow to sepcify globals/locals
for eval, and reduced ROM usage by >100 bytes on stmhal and unix.

Also, the call to mp_parse_compile_execute is tail call optimised for
the import code, so it doesn't increase stack memory usage.

This should pretty much resolve issue #50.

Addresses issue #864.

It seems most sensible to use size_t for measuring "number of bytes" in
malloc and vstr functions (since that's what size_t is for).  We don't
use mp_uint_t because malloc and vstr are not Micro Python specific.

Stack is full descending and must be 8-byte aligned.  It must start off
pointing to just above the last byte of RAM.

Previously, stack started pointed to last byte of RAM (eg 0x2001ffff)
and so was not 8-byte aligned.  This caused a bug in combination with
alloca.

This patch also updates some debug printing code.

Addresses issue #872 (among many other undiscovered issues).

Part of code cleanup, working towards resolving issue #50.

Part of code cleanup, working towards resolving issue #50.

Part of code cleanup, to resolve issue #50.

This way, the native glue code is only compiled if native code is
enabled (which makes complete sense; thanks to Paul Sokolovsky for
the idea).

Should fix issue #834.

qstr_init is always called exactly before mp_init, so makes sense to
just have mp_init call it.  Similarly with
mp_init_emergency_exception_buf.  Doing this makes the ports simpler and
less error prone (ie they can no longer forget to call these).

See discussion in issue #50.

As stack checking is enabled by default, ports which don't call
stack_ctrl_init() are broken now (report RuntimeError on startup). Save
them trouble and just init stack control framework in interpreter init.

One thing is wanting to do 1 / 2 and get something else but 0, and quite
another - doing rocket science ;-).

Benefits: won't crash baremetal targets, will provide Python source location
when not implemented feature used (it will no longer provide C source
location, but just grep for error message).

- Move the includes for alloca() intp mpconfigport.h

This saves 4 words of stack space per Python call.

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

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.

Also unifies use of SMALL_INT_FITS macro across parser and runtime.

Addresses issue #627.

See issue #608 for justification.

Debugging output for emit_glue now simplified so that the init and
deinit functions are no longer needed.

__debug__ now resolves to True or False.  Its value needs to be set by
mp_set_debug().

TODO: call mp_set_debug in unix/ port.

TODO: optimise away "if False:" statements in compiler.

This is better than forcing each getiter() implementation to raise exception.

This was hit when trying to make urlparse.py from stdlib run. Took
quite some time to debug.

TODO: Reconsile bound method creation process better, maybe callable is
to generic type to bind at all?

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

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/.