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/DeclPrinter.cpp b/clang/lib/AST/DeclPrinter.cpp
index c3ce476..0ea946d 100644
--- a/clang/lib/AST/DeclPrinter.cpp
+++ b/clang/lib/AST/DeclPrinter.cpp
@@ -96,7 +96,7 @@
     void prettyPrintAttributes(Decl *D);
     void printDeclType(QualType T, StringRef DeclName, bool Pack = false);
   };
-}
+} // namespace
 
 void Decl::print(raw_ostream &Out, unsigned Indentation,
                  bool PrintInstantiation) const {