[gardening] C++ gardening: Terminate namespaces, fix argument names, ...

Changes:
* Terminate all namespaces with the correct closing comment.
* Make sure argument names in comments match the corresponding parameter name.
* Remove redundant get() calls on smart pointers.
* Prefer using "override" or "final" instead of "virtual". Remove "virtual" where appropriate.

unittests/Basic/BlotMapVectorTest.cpp

@@ -329,7 +329,7 @@ public:
     EXPECT_TRUE(!ConstructedTesters->hasLiveTesters());
   }
 
-  ~BlotMapVectorTest() {
+  ~BlotMapVectorTest() override {
     ConstructedTesters->verifyTesters();
     llvm::outs() << "Destroying Fixture\n";
     ConstructedTesters->finalize();