pidgin/purple-plugin-pack

updated the pkg-config macros to use libpurple-3 and pidgin-3
[Napster Protocol Plugin]
type=default
depends=purple
provides=napster
summary=NAPSTER Protocol Plugin
description=%(summary)s
authors=Rob Flynn
introduced=1.0beta6
notes=Introduced into the Purple Plugin Pack after it was removed from libpurple.