[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/Transforms/SpeculativeDevirtualizer.cpp

@@ -534,7 +534,7 @@ namespace {
   /// class is at the bottom of the class hierarchy.
   class SpeculativeDevirtualization : public SILFunctionTransform {
   public:
-    virtual ~SpeculativeDevirtualization() {}
+    ~SpeculativeDevirtualization() override {}
 
     void run() override {
       ClassHierarchyAnalysis *CHA = PM->getAnalysis<ClassHierarchyAnalysis>();