Enabling 3DNow! prefetch instruction support for a few AMD processors in the
clang front end. This change will allow the __PRFCHW__ macro to be set on these
processors and hence include prfchwintrin.h in x86intrin.h header. Support for
the intrinsic itself seems to have already been added in r178041.

Differential Revision: http://llvm-reviews.chandlerc.com/D1934



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@192829 91177308-0d34-0410-b5e6-96231b3b80d8