Obtained from: partly from an ancient patch of mine via 1.1.5

Obtained from:	partly from an ancient patch of mine via 1.1.5

Temporarily nuke TS_WOPEN.  It was only used for the obscure MDMBUF
flow control option in the kernel and for informational purposes
in `pstat -t'.  The latter worked properly only for ptys.  In
general there may be multiple processes sleeping in open() and
multiple processes that successfully opened the tty by opening it
in O_NONBLOCK mode or during a window when CLOCAL was set.  tty.c
doesn't have enough information to maintain the flag but always
cleared it in ttyopen().

TS_WOPEN should be restored someday just so that `pstat -t' can
display it (MDMBUF is already fixed).  Fixing it requires counting
of processes sleeping in open() in too many serial drivers.