app: change gimp_image_crop() to use x, y, width, height

tools/pdbgen/pdb/image_transform.pdb

@@ -195,7 +195,7 @@ HELP
     success = FALSE;
   else
     gimp_image_crop (image, context,
-                     offx, offy, offx + new_width, offy + new_height,
+                     offx, offy, new_width, new_height,
                      TRUE);
 }
 CODE

tools/pdbgen/pdb/plug_in_compat.pdb

@@ -309,7 +309,7 @@ HELP
         }
 
       gimp_image_crop (image, context,
-                       x1, y1, x2, y2, TRUE);
+                       x1, y1, x2 - x1, y2 - y1, TRUE);
 
       gimp_image_undo_group_end (image);
     }