Add -mqpx and -mno-qpx feature flags to toggle use of the PPC QPX vector instruction set

I've renamed the altivec test to ppc-features (because now there is more than one feature to test).

llvm-svn: 174204
diff --git a/clang/lib/Driver/Tools.cpp b/clang/lib/Driver/Tools.cpp
index 18b49e6..c539216 100644
--- a/clang/lib/Driver/Tools.cpp
+++ b/clang/lib/Driver/Tools.cpp
@@ -1091,6 +1091,11 @@
     CmdArgs.push_back("-target-feature");
     CmdArgs.push_back("-altivec");
   }
+
+  if (Args.hasFlag(options::OPT_mno_qpx, options::OPT_mqpx, false)) {
+    CmdArgs.push_back("-target-feature");
+    CmdArgs.push_back("-qpx");
+  }
 }
 
 void Clang::AddSparcTargetArgs(const ArgList &Args,