1. the mask is passed by value, not by reference
2. compare the rest of the mask bits not the valid ones
3. return 0, not the current fd's flags.
Now appletviewer works on an inet display. It will not work
with :0 because /tmp/.X11-pipe/X0 is a named pipe, not a
socket like our /tmp/.X11-unix/X0. Maybe I'll kludge svr4_sys_open
to return an fd to a unix socket when someone attempts to call
open on a unix socket.
