mark btn4ws as executable

port to gimp-2.6 API (fixes #18)

btn4ws.py

@@ -40,7 +40,7 @@ pdb = gimp.pdb
 
 btn4ws_version = "0.8.0"
 
-logging.basicConfig(level=logging.DEBUG,
+logging.basicConfig(level=logging.WARN,
                     format='%(asctime)s %(levelname)s %(message)s',
                     stream=sys.stderr)
 
@@ -989,7 +989,7 @@ class btn4wsplugin(gimpplugin.plugin):
             image.add_layer(blackboard, len(image.layers))
             selectionall(image)
             if transparency:
-                blackboard.preserve_trans = True
+                blackboard.lock_alpha = True
                 editclear(blackboard)
             else:
                 gimp.set_background(bgcolor)