Initial version of Go bindings.

This code is based on the existing LLVM Go bindings project hosted at:
https://github.com/go-llvm/llvm

Note that all contributors to the gollvm project have agreed to relicense
their changes under the LLVM license and submit them to the LLVM project.

Differential Revision: http://reviews.llvm.org/D5684

llvm-svn: 219976