Auto merge of #957 - matttproud:support/netbsd/terminal-ioctl, r=alexcrichton

netbsdlike: add TIOCSCTTY and TIOCSWINSZ ioctls.

Include ioctl commands for becoming controlling tty and setting window
size.  This enables https://github.com/jwilm/alacritty to be built and
run on OpenBSD 6.3.  NetBSD and kin share the same command constants.