add missing header end comments

- ensures a consistent usage in header files
- also add a blank line after the copyright header where missing
- also remove orphan new-lines at the end of some files

src/util.h

@@ -222,4 +222,4 @@ template <typename Callable> void TraceThread(const char* name,  Callable func)
     }
 }
 
-#endif
+#endif // BITCOIN_UTIL_H