games/iourbanterror: point to proper pkg-descr

games/iourbanterror ships its own pkg-descr file, but does not define
DESCR, so pkg-descr from its parent port, games/ioquake3, is used.

Define DESCR to point to the proper file for games/iourbanterror and
games/iourbanterror-server.

While here, fix tabs/space mix in intendation and drop trailing whitespace
as pointed by portlint.