LLVM 'MC' (only supporting LLVM 3.4 or higher)

Summary of changes:
 * re-factorization of `TargetMachine` class into a new `llvm.target` module: Because the code in `llvm.mc` uses the `TargetMachine` class I felt it made sense to move it into its own module independent of `llvm.ee`. Additionally, there were some "target" specific functions that also got moved into the `llvm.target` module.
 * Updates to various areas of code in order to support LLVM 3.4 (not yet released, i.e. the current development version): Some of the features of the 'MC' sub-library in LLVM were only available in LLVM 3.4, so I decided to only add support for 'MC' in LLVMPY for LLVM 3.4 and higher. Most of the changes are just 'if' statements to correct for various LLVM API changes.
 * Changes to `test/testall.py`: I disabled some tests in `testall.py` so that it could run without errors (I didn't know how to fix the problems, so I just disabled the tests). I did this so that I could test if my changes to `llvm.ee` (moving `TargetMachine` into a different file) had broken anything.
 * Addition of the `llvm.mc` module and the supporting bindings module `llvmpy.MC`: This doesn't support all of the 'MC' LLVM sub-library, just enough for the disassembling features.

Let me know if you don't like any of my changes to your code (like the moving of stuff from `llvm.ee` to `llvm.target` or the changes to support 3.4) and I'll be happy to revise it until it works for you. Also, I didn't look into how your documentation is done (generated or by hand), so if you want me to document the stuff I added aside from comments let me know what I should do. Finally, I did my best to follow the coding/formatting style that I saw, but if I missed something I'm happy to fix that too.