Replace a few more "fall through" comments with LLVM_FALLTHROUGH

Follow up to r278902. I had missed "fall through", with a space.

llvm-svn: 278970
diff --git a/llvm/lib/Support/raw_ostream.cpp b/llvm/lib/Support/raw_ostream.cpp
index 275fe1d..c4a7b14 100644
--- a/llvm/lib/Support/raw_ostream.cpp
+++ b/llvm/lib/Support/raw_ostream.cpp
@@ -344,10 +344,10 @@
   // Handle short strings specially, memcpy isn't very good at very short
   // strings.
   switch (Size) {
-  case 4: OutBufCur[3] = Ptr[3]; // FALL THROUGH
-  case 3: OutBufCur[2] = Ptr[2]; // FALL THROUGH
-  case 2: OutBufCur[1] = Ptr[1]; // FALL THROUGH
-  case 1: OutBufCur[0] = Ptr[0]; // FALL THROUGH
+  case 4: OutBufCur[3] = Ptr[3]; LLVM_FALLTHROUGH;
+  case 3: OutBufCur[2] = Ptr[2]; LLVM_FALLTHROUGH;
+  case 2: OutBufCur[1] = Ptr[1]; LLVM_FALLTHROUGH;
+  case 1: OutBufCur[0] = Ptr[0]; LLVM_FALLTHROUGH;
   case 0: break;
   default:
     memcpy(OutBufCur, Ptr, Size);