Add custom buttoms with the zoom buttoms

```
It could be much useful to add custom buttoms in the VNC interface to use it
when the zoom buttoms appear. With these buttoms we can send keys like cursors
or a secuence of keys (Ctrl+alt+del). If you also add profiles and a key to
pass through profiles you can forget Send key menu.

Thank you very much for these application.

```

Original issue reported on code.google.com by `efrenlop...@gmail.com` on 25 Nov 2010 at 12:46