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

llvm-svn: 304651
diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
index d9528be..acacdc2 100644
--- a/clang/lib/Sema/SemaDeclCXX.cpp
+++ b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -14639,6 +14639,7 @@
   case EST_ComputedNoexcept:
     if (!Finder.TraverseStmt(Proto->getNoexceptExpr()))
       return true;
+    LLVM_FALLTHROUGH;
     
   case EST_Dynamic:
     for (const auto &E : Proto->exceptions()) {