Comment Sema: Make most of CommentSema private (NFC)

We only need to expose setDecl, copyArray and the actOn* methods.

clang/include/clang/AST/CommentSema.h

@@ -181,6 +181,7 @@ public:
 
   FullComment *actOnFullComment(ArrayRef<BlockContentComment *> Blocks);
 
+private:
   void checkBlockCommandEmptyParagraph(BlockCommandComment *Command);
 
   void checkReturnsCommand(const BlockCommandComment *Command);