[PowerPC] Fix SSE translation on FreeBSD

This patch drops throws specifier in posix_memalign declaration because
that's different between glibc and other libc, and Clang has a hack.

Differential Revision: https://reviews.llvm.org/D117972

(cherry picked from commit f2f4080)

clang/lib/Headers/ppc_wrappers/mm_malloc.h

@@ -19,7 +19,7 @@
 #ifndef __cplusplus
 extern int posix_memalign (void **, size_t, size_t);
 #else
-extern "C" int posix_memalign (void **, size_t, size_t) throw ();
+extern "C" int posix_memalign (void **, size_t, size_t);
 #endif
 
 static __inline void *