[PATCH] [PowerPC] Initial VSX intrinsic support, with min/max for vector double

[hfinkel at anl.gov]

I'd like to change the existing error message for use of double with __vector to also say something like, "; did you intend compile for the POWER7?"

Instead of adding a new overload, I think it would be better to just move the necessary type-checking logic into DeclSpec::Finish. DeclSpec::Finish already gets a Preprocessor &PP argument, and Preprocessor has a getTargetInfo function that you can use. The current scheme which depends on knowing to call the correct overload when adding DeclSpec::TST_double seems very fragile.

http://reviews.llvm.org/D5949