Add llvm_unreachable at end of fully covered switch to pacify GCC.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@179753 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/clang/Sema/ScopeInfo.h b/include/clang/Sema/ScopeInfo.h
index a48422a..103ce82 100644
--- a/include/clang/Sema/ScopeInfo.h
+++ b/include/clang/Sema/ScopeInfo.h
@@ -529,6 +529,7 @@
     case CR_Default:
       return "default captured statement";
     }
+    llvm_unreachable("Invalid captured region kind!");
   }
 
   static bool classof(const FunctionScopeInfo *FSI) {