Pull in r201784 from upstream llvm trunk (by Benjamin Kramer):

  AsmParser: Disable Darwin-style macro argument expansion on non-darwin targets.

  There is code in the wild that relies on $0 not being expanded.

This fixes some cases of using $ signs in literals being incorrectly
assembled.

Reported by:	Richard Henderson
Upstream PR:	http://llvm.org/PR21500
MFC after:	3 days