Added LLVM_FALLTHROUGH to address warning: this statement may fall through. NFC.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@304477 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Parse/ParseInit.cpp

@@ -501,7 +501,8 @@ bool Parser::ParseMicrosoftIfExistsBraceInitializer(ExprVector &InitExprs,
     Diag(Result.KeywordLoc, diag::warn_microsoft_dependent_exists)
       << Result.IsIfExists;
     // Fall through to skip.
-      
+    LLVM_FALLTHROUGH;
+
   case IEB_Skip:
     Braces.skipToEnd();
     return false;