Fixes #K open

You need to process omode with openmode() before doing an equality check
with OREAD/O_RDONLY (which == 0, btw...).

This was breaking the ability to bind #K or bind -b.  bind -a worked.
Similarly, ls \#K failed, but cat \#K worked.  The ls-cat check is the
usual way to detect this stuff (it's come up before).