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

xpcom/components/ManifestParser.cpp

@@ -171,7 +171,7 @@ struct AutoPR_smprintf_free
   char* mBuf;
 };
 
-} // anonymous namespace
+} // namespace
 
 /**
  * If we are pre-loading XPTs, this method may do nothing because the
@@ -465,7 +465,7 @@ struct CachedDirective
   char* argv[4];
 };
 
-} // anonymous namespace
+} // namespace
 
 
 /**