Altering base virtual for virtual/gnustep from gnustep-back-xlib to gnustep-back...

Altering base virtual for virtual/gnustep from gnustep-back-xlib to gnustep-back-art because vapier keeps removing my entry for -art from default-linux/virtuals _where it belongs_ (i have no means to test non-linux based platforms) because the virtual (set to the -xlib one) is already in profiles/base ... though default-linux/virutals says '# Use this virtuals file to either overload the base profile's defined # virtuals, or add virtuals that are specific to this family of profiles' and generally I thought that that is what cascasing profiles where for, i guess we're ignoring that now.  Excuse my pissiness, but this is about the 3rd time I've had to make changes caused by being surpised, without even an email saying 'hey man, i'm monkeying with this wacky gnustep stuff you put in here, and it's likely gonna break your ebuilds -- but whatever -- problem solved.