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

llvm-svn: 304641
diff --git a/clang/lib/Analysis/PrintfFormatString.cpp b/clang/lib/Analysis/PrintfFormatString.cpp
index ed7193e..6055669 100644
--- a/clang/lib/Analysis/PrintfFormatString.cpp
+++ b/clang/lib/Analysis/PrintfFormatString.cpp
@@ -441,6 +441,7 @@
       case LengthModifier::AsShort:
         if (Ctx.getTargetInfo().getTriple().isOSMSVCRT())
           return Ctx.IntTy;
+        LLVM_FALLTHROUGH;
       default:
         return ArgType::Invalid();
     }