gdk thread locking for album art

use gdk.threads_enter() and gdk.threads_leave() to lock the album art
changing section of the AlbumArt class.

ocarina/image.py

@@ -1,6 +1,7 @@
 # Bryan Schumaker (10/24/2010)
 import libsaria
 import gtk
+gdk = gtk.gdk
 
 from libsaria import threads
 
@@ -38,13 +39,13 @@ class AlbumArt(Image):
 		self.file = "images/ocarina.png"
 
 	def set(self, file=None):
-		lock.acquire()
+		gdk.threads_enter()
 		if file != None:
 			self.file = file
 		self.set_from_file(self.file)
 		self.set_height(64)
 		self.show()
-		lock.release()
+		gdk.threads_leave()
 
 	def set_height(self, new_h):
 		size = self.size_request()