[PATCH] Add AnyReg calling convention support for patchpoint intrinsic.

[Andrew Trick]

  That's a lot of work! I have two concerns:

  (1) I would prefer not duplicating most of the functionality in InstrEmitter::EmitMachineNode. It looks like we mainly need to special case the call to CreateVirtualRegisters.

  (2) I don't think we can reserve a register for patching by defining a regmask (CSR_AnyReg_64_SaveList). (I changed my mind). I think we need to add an implicit-def with an early clobber flag to prevent any args/live values from being allocated to the scratch reg.

http://llvm-reviews.chandlerc.com/D2009