Merge pull request #353 from rjdowdall/master

Some math functions
stmhal: Add accelerometer driver; fix bug with LFN.
Merge branch 'master' of github.com:micropython/micropython
Rename test so that it doesn't clash with Python math module.
Implement str.partition and add tests for it.
Implement str.rpartition and add tests for it.
str.(r)partition: factor out duplicate code.

Switch str.rpartition to search from left to right. Factor the
duplicate code into one helper function.
py: Implement parsing of infinity and nan for floats.
py: Allow 'complex()' to take a string as first argument.
py: Improve mp_parse_num_integer; make it self contained.
Merge pull request #351 from xbe/str-partition

Implement str.partition and add tests for it.
py: Make str.[r]partition more efficient.
py: Put back proper ValueError for badly parsed integers.
Disable some math functions until they work correctly.
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.