Make 'set offset from cursor' group operator internal.

This operator relies on a rather specific context setup, so it shall not
be exposed to user in 'operator search' menu etc.

Based on D2528 by Vuk Gardašević (lijenstina).

release/scripts/startup/bl_operators/object.py

@@ -864,7 +864,7 @@ class DupliOffsetFromCursor(Operator):
     """Set offset used for DupliGroup based on cursor position"""
     bl_idname = "object.dupli_offset_from_cursor"
     bl_label = "Set Offset From Cursor"
-    bl_options = {'REGISTER', 'UNDO'}
+    bl_options = {'INTERNAL', 'UNDO'}
 
     @classmethod
     def poll(cls, context):