client: Include poll.h instead of sys/poll.h
client: Include poll.h instead of sys/poll.h

POSIX mandates the poll.h header as the standard location of poll(2).

sir-murray/wayland,sir-murray/wayland,abooij/wayland,eyolfson/wayland,mchalupa/wayland,mchalupa/wayland,bitfactor/wayland,bitfactor/wayland,abooij/wayland,tulcod/wayland,sir-murray/wayland,eyolfson/wayland,bitfactor/wayland,abooij/wayland,tulcod/wayland,tulcod/wayland,eyolfson/wayland,mchalupa/wayland