Qt: small header changes / fixes

- ensure header inclusion guard is named after the header file
- add missing comments at the end of some inclusion guards
- add a small Qt5 compatibility fix in macdockiconhandler.h

src/qt/transactiontablemodel.h

@@ -81,5 +81,4 @@ public slots:
     friend class TransactionTablePriv;
 };
 
-#endif
-
+#endif // TRANSACTIONTABLEMODEL_H