Minor change to include default CTR button.

The developer says that he uses two IDs for the button as there are two possible ways of having the button.

"ctr_appbutton2" is the default button only for Windows in the titlebar.
"ctr_appbutton" is for the toolbar button that can be dragged virtually anywhere (including where the default one is) and is an icon instead of text.

Sorry about that, I didn't realise there were two IDs.