spc: Remove plugin

Submitted by Sebastian Dröge @slomo

Link to original bug (#774568)

Description

commit 8ad3f148
Author: Sebastian Dröge sebastian.droege@collabora.co.uk
Date: Sat Aug 8 21:17:37 2009 +0200

spc: Add the OpenSPC spc plugin again  
  
The gme plugin obsoletes it but it might still be useful  
for users that don't have gme yet or prefer openspc for some reason.  

Let's get rid of it now?