Man pages matching name al_fwrite16be in section 3alleg5:

al_fwrite16be.3alleg5.en	debian 10 / allegro5-doc
al_fwrite16be.3alleg5.en	debian 11 / allegro5-doc
al_fwrite16be.3alleg5.en	debian 12 / allegro5-doc
al_fwrite16be.3alleg5.en	debian 13 / allegro5-doc