Add an explicit `LLVM_FALLTHROUGH` annotation to an intentional

fallthrough. Fixes GCC and Clang warnings about this.

llvm-svn: 321392

clang/lib/Sema/SemaType.cpp

@@ -3143,6 +3143,7 @@ static void warnAboutRedundantParens(Sema &S, Declarator &D, QualType T) {
     case DeclaratorChunk::Paren:
       if (&C == &Paren)
         continue;
+      LLVM_FALLTHROUGH;
     case DeclaratorChunk::Pointer:
       StartsWithDeclaratorId = false;
       continue;