Fixed/added namespace ending comments using clang-tidy. NFC

The patch is generated using this command:

  $ tools/extra/clang-tidy/tool/run-clang-tidy.py -fix \
      -checks=-*,llvm-namespace-comment -header-filter='llvm/.*|clang/.*' \
      work/llvm/tools/clang

To reduce churn, not touching namespaces spanning less than 10 lines.

llvm-svn: 240270
diff --git a/clang/lib/AST/ItaniumMangle.cpp b/clang/lib/AST/ItaniumMangle.cpp
index e5a31f8..38c3ccb 100644
--- a/clang/lib/AST/ItaniumMangle.cpp
+++ b/clang/lib/AST/ItaniumMangle.cpp
@@ -408,7 +408,7 @@
   void mangleFunctionParam(const ParmVarDecl *parm);
 };
 
-}
+} // namespace
 
 bool ItaniumMangleContextImpl::shouldMangleCXXName(const NamedDecl *D) {
   const FunctionDecl *FD = dyn_cast<FunctionDecl>(D);