New headers

Removed point.h and point.c

defines.h
POINT defined here
errors enum
directions enum
MIN, MAX macros

board.h:
Changed board_t struct
create_board() -> board_init()
to_string() -> board_display (from game.h)
set_state() -> board_set_point() from (point.h)
get_state() -> board_get_point() from (point.h)

move.h
get_random_player_move() removed
get_score() logic changed and private (from game.h)
get_strength() logic changed and private
undo_move() private
min_value() private

game.h
get_window() new/private
winner_is() logic changed