(interact): Renamed the class abstract_interact. Added methods
get_attributes and set_attributes.

* src/interact.h (window_change_callback): New class.
(abstract_interact): Replaced the window_change method with to
methods, window_size and window_change_subscribe.

* src/interact.c: Moved unix_interact class to unix_interact.c.

Rev: src/interact.c:1.4
Rev: src/interact.h:1.4