[PATCH] CodeGen: implement __emit and __yield intrinsics

[Reid Kleckner]

>>! In D3489#14, @abdulras wrote:
> @rnk, Im a bit confused here.  Why do I need the I constraint for `__emit`?  Isnt **I** an immediate integer valid for a data operation?  The __emit takes an unsigned long and emits that long constant as an instruction.

I was imagining this implementation in intrin.h:
  #define __emit(__x) __asm __volatile (".long %0" : "i"(__x))

But it sounds like this may need to be a builtin if Windows SDK headers are using it, so this comment isn't particularly relevant.

http://reviews.llvm.org/D3489