[9fans] fix to /sys/src/ape/lib/bsd/pty.c

[geoff@collyer.net]

In the course of trying to get rk to build, I had to get the APE
_getpty() working again.  The new close and remove may be excessively
paranoid, but the changes from `3' to `O_RDWR' are essential.


: cpu; diff `{yesterday .} pty.c
66c66
< 	fd = _OPEN(fssrv, 3);
---
> 	fd = _OPEN(fssrv, O_RDWR);
67a68,77
> 		/*
> 		 * remove fssrv here, if it exists, to avoid a race
> 		 * between the loop in the default case below and the
> 		 * new ptyfs removing fssrv when it starts.
> 		 * we otherwise might be unlucky enough to open the old
> 		 * (hung channel) fssrv before ptyfs removes it and break
> 		 * out of the loop with an open fd to a hung channel?
> 		 */
> 		close(fd);
> 		remove(fssrv);
78c88
< 				fd = _OPEN(fssrv, 3);
---
> 				fd = _OPEN(fssrv, O_RDWR);
88c98,99
< 		_MOUNT(fd, "/dev", MAFTER, "");
---
> 		if (_MOUNT(fd, "/dev", MAFTER, "") < 0)
> 			;		/* buggery */