[llvm.py] Initial skeleton for Python LLVM bindings

This contains a semi-functional skeleton for the implementation of the
LLVM bindings for Python.

The API for the Object.h interface is roughly designed but not
implemented. MemoryBufferRef is implemented and actually appears to
work!

The ObjectFile unit test fails with a segmentation fault because the
LLVM library isn't being properly initialized. The build system doesn't
know about this code yet, so no alerts should fire.

llvm-svn: 152397