[PPC] Implement VLE support

[Rot127]

There has been the request already to add PowerPC VLE support to Capstone (#560).

With the auto-sync update this becomes now easier to add.

The steps to add this is:

• Extend the PPC definitions in LLVM with a td file for VLE.
  • A simple example how to do this is the PS extension which is also not upstreamed in LLVM but only added by us.
  • Someone already attempted to add it. Maybe he has already some work done we could use?
• If any new operand types are necessary, implement the decoder and printer functions in PPCDisassembler.cpp and PPCAsmPrinter.cpp
• Run auto-sync updater to get it into Capstone.

Good start is the auto-sync docs and linked docs in there. It gives more details about the process and how everything works.