Adding support for an LLVM-supported architecture?

[jfktrey]

Using MIPS as a reference, I checked what was required for supporting an architecture. It seems that, other than the llvm includes (which I assume are pulled straight from the project), there are only a few other areas of work that are required:

1. Adding the definitions for the architecture to common files (ex. keystone.h)
2. Adding references to the target in build scripts
3. Adding bindings for supported languages
4. Adding test scripts

If I were to add support for a target, is there anything else required that I'm missing?

[jfktrey]

PR in #392