Man pages matching name al_add_new_bitmap_flag in section 3alleg5:

al_add_new_bitmap_flag.3alleg5.en	debian 10 / allegro5-doc
al_add_new_bitmap_flag.3alleg5.en	debian 11 / allegro5-doc
al_add_new_bitmap_flag.3alleg5.en	debian 12 / allegro5-doc