Mbufferio

------
- expose utility function "murmur128"

------
- expose utility functions "make_utf8, make_unicode, umurmur128"

------
- fix: memoryview(MBufferIO()) used to raise BufferError

------
- fix: simple MBUfferIO() raised a TypeError

--------------
- Allow to make MBufferIO objects from memory views that have been built by PyMemoryView_FromMemory() or PyMemoryView_FromBuffer().

------
- Added a "from_mview" class method.