Added nb_lines in Data, slightly modified a few functions prototypes.
All drawing funtions take the number of lines into account. Don't set nb_lines over 32.
Finally correctly implemented the transition when changing the number of lines. Currently only for the diagonals, but the changes are coming for the walls and the player.
The draw_player function now supports the line transitions.
Minor fixes, added some comments
Started implementing the Level support
Forgot to create a new branch, next changes will be on the Level branch.