moductypes: Remove debug inclusion of stdio.h .
py: mp_buffer_info_t::buf may be valid, but NULL for empty objects.

This happens for example for zero-size arrays. As .get_buffer() method now
has explicit return value, it's enough to distinguish success vs failure
of getting buffer.
objarray: Implement equality testing between arrays and other buffers.
tools, gendoc: Output small descr about module TOC.
stmhal: Add sys.platform string to PYBv1.0 (it's "pyboard").
doc: Document gc, sys, math, cmath.
doc: Fix up a few docs in sys module.
modsocket: .recv() returns bytes object.
py: binary.c: Properly implement alignment for native unpacked structs.
objstr: split(): check arg type consistency (str vs bytes).

Similar to other methods and following CPython3 strictness.
stmhal: Working STM32F4DISC accelerometer, via Python script.

Thanks to David Siorpaes.
Merge branch 'master' of github.com:micropython/micropython
objstr: Make sure that bytes are indexed as bytes, not as unicode.

Fixes #795.
py, modcmath: Fix doc comment, and add some more of them.
py, objstr: Optimise bytes subscr when unicode is enabled.

Saves code bytes and makes it faster, so why not?