added tests for rbw_get_ack* functions
added tests for rbw_inc_head*
add tests for rbw_set_win_size
Added tests for ringbufferwindow

Unit tests added:
* rbw_get_ack_n
* rbw_get_get_ack_of_packet
* rbw_inc_head
* rbw_inc_head_to_packet
* rbw_set_win_size