Add C API for specifying CPU to the disassembler.

It was a nasty oversight that we didn't include this when we added this
API in the first place. Blech.

rdar://12839439

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@169653 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed