[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.

lib/SILOptimizer/LoopTransforms/LoopUnroll.cpp

@@ -67,7 +67,7 @@ protected:
   }
 };
 
-} // End anonymous namespace.
+} // end anonymous namespace
 
 void LoopCloner::cloneLoop() {
   auto *Header = Loop->getHeader();
@@ -457,7 +457,7 @@ class LoopUnrolling : public SILFunctionTransform {
   }
 };
 
-} // end anonymous namespace.
+} // end anonymous namespace
 
 SILTransform *swift::createLoopUnroll() {
   return new LoopUnrolling();