Making Pidgin small-screen-friendly

[Casey Ho]

I played around with the Add Buddy Pounce dialog some, and placed the
options in the "Pounce When Buddy" into 4 columns instead of two.

* The dialog height is under 580px.
* On a 540px screen the add/cancel buttons are readable and usable, so
no functionality is lost.  * Increasing to 4 columns does not widen
the dialog (with English)

The four column list is readable and actually works well- probably
because the side-by-side items share the same usage.

See screenshot at http://caseyho.com/misc/pidgin/

-Casey