connection.c: Align pointer extra storage correctly
connection.c: Align pointer extra storage correctly

Most extra data are just pointers, but in case of fds we store an int in
the extra space.  That can cause un-aligned access to pointers on 64 bit
architectures.  Make sure we always align pointer storage correctly.

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