Keypad fixes

Two things here : 

1) KeyEvent send the same code for DEL and keypad DEL (`.`) keys, regardless to numlock mode.
This fix it, allowing the keypad DEL key to actually send a `.`.

2) Switch keypad handling to xterm PC-Style, as does Gnome Terminal and Konsole (and of course, xterm)
See : http://www.xfree86.org/current/ctlseqs.html#PC-Style%20Function%20Keys