Missing ALLEGRO_ constants

[katastic]

There are missing constants that I've had to look up in the Allegro headers and define myself. For example:

int ALLEGRO_PIXEL_FORMAT_ANY = 0; int ALLEGRO_VSYNC = 26; int ALLEGRO_MAX_BITMAP_SIZE = 27;

(p.s. Thanks for the hard work!)

[rcorre]

These all seem to be defined:

• https://github.com/SiegeLord/DAllegro5/blob/master/allegro5/color.d#L15
• https://github.com/SiegeLord/DAllegro5/blob/master/allegro5/display.d#L58
• https://github.com/SiegeLord/DAllegro5/blob/master/allegro5/display.d#L59