illumos gate

ptsl and ptc appear to implement the old BSD-style ptys (much credit to Josh for working that out).

Their sources, in usr/src/uts/common/io/tty_pty.c and usr/src/uts/common/io/tty_pts.c, and usr/src/uts/common/io/tty_ptyconf.c. Should make it clear that they have nothing to do with the modern pseudo tty implementation involving /dev/pts and /dev/ptmx (where by "modern", it has likely existed since at least 1990). That stuff is in pts.c, ptm.c, and ptms_conf.c

It would perhaps even be worth having sub-directories for each (pty and oldpty?), if that wasn't too much trauma with Makefiles

Note that usr/src/uts/common/io/tty_common.c is used by other things, and is fine.