events_callback_set is deprecated and x and y coordinates in mouse events now is relative to element

+ further work to bring events_callback_set functionality to event_register
  events_callback_set is deprecated but it is still working. Now can be used
  event_register only without events_callback_set.
  In the future events_callback set will be removed.
+ x and y coordinates in mouse events now counted from top and left element which is target of event