Expose __builtin_bswap16.

GCC has always supported this on PowerPC and 4.8 supports it on all platforms,
so it's a good idea to expose it in clang too. LLVM supports this on all targets.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@165362 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/CodeGen/builtins.c b/test/CodeGen/builtins.c
index 65b9ad1..9ba12bb 100644
--- a/test/CodeGen/builtins.c
+++ b/test/CodeGen/builtins.c
@@ -113,6 +113,7 @@
 
   // Whatever
 
+  P(bswap16, (N));
   P(bswap32, (N));
   P(bswap64, (N));
   // FIXME