Bug 1182996 - Fix and add missing namespace comments. rs=ehsan

The bulk of this commit was generated by running:

  run-clang-tidy.py \
    -checks='-*,llvm-namespace-comment' \
    -header-filter=^/.../mozilla-central/.* \
    -fix

toolkit/components/reflect/reflect.h

@@ -24,7 +24,7 @@ private:
   ~Module();
 };
 
-}
-}
+} // namespace reflect
+} // namespace mozilla
 
 #endif