Man pages matching name get_vector_rotation_quat in section 3alleg4:

get_vector_rotation_quat.3alleg4.en	debian 10 / allegro4-doc
get_vector_rotation_quat.3alleg4.en	debian 11 / allegro4-doc
get_vector_rotation_quat.3alleg4.en	debian 12 / allegro4-doc