caca: Cleanups and fixes

Submitted by Priit Laes @plaes

Link to original bug (#599018)

Description

Created attachment 145832
0001-Exit-properly-when-invalid-driver-has-been-selected.patch

Currently, when specifying a driver that doesn't exist causes crash in
cacasink.

Patch 145832, "0001-Exit-properly-when-invalid-driver-has-been-selected.patch":
0001-Exit-properly-when-invalid-driver-has-been-selected.patch