Forgot to move the contextual definition of ScreenSegmentChanged when it's arguments were made mutable and mostly serial.
1. reverting last change
2. adding comment to the shared StateMachine regarding the definition of mutable
3. adding proper ack logic to ScreenSegmentChanged client side event handler
4. Prefiltering screen segment changes for buffer updates before locking the I/O channel
5. Updating args for the screen segment update when a clone reference is created and saved off for future change merges