Revision 437664

- Use posix_openpt(2) instead of opening /dev/ptmx which requires
  loading an extra kernel module on FreeBSD 10.0+
- Add LICENSE_FILE
- Remove the unnecessary KMODDIR knob

PR:		217880
Approved by:	mat (mentor), maintainer timeout (2 weeks+)
Differential Revision:	https://reviews.freebsd.org/D10243