Added ZeroDivisionError to float division.
objint_longlong: Add regression test for improper inplace op implementation.
objstr: Switch from in-object string data to ptr to separate memory area.

This is pre-requisite for having efficient implementation of str<->bytes
conversion, and having that efficient is required with unfortunare
str vs bytes dichotomy in Python3.
py: Make 'str' be a proper type, support standard constructor args.
py: Make 'bytes' be a proper type, support standard constructor args.
Merge pull request #355 from pfalcon/str-bytes-types

Make str and bytes be proper types
stmhal: Add support for USB MSC device.

This gives a functioning, independent MSC device.
Merge branch 'master' of github.com:micropython/micropython
Implement __aeabi_f2d and __aeabi_d2f
showbc: Dump YIELD_FROM.
Merge remote-tracking branch 'upstream/master'
stmhal: USB CDC and MSC device work together.
Merge branch 'master' of github.com:micropython/micropython
stmhal: Tidy up USB device configuration.  Make it use less RAM.
sthmal: Remove obsolete files.
stmhal: Tidy up USB CDC+MSC device some more.
stmhal: Add PYBv10 config; add RNG support.
Fixed broken math functions that return bool and added some more.
stmhal: Add os module with a few basic functions.
stmhal: Add time module with sleep function.