Remove linux specific calls

Docker-DCO-1.1-Signed-off-by: Guillaume J. Charmes <guillaume.charmes@docker.com> (github: creack)
Add Freebsd client support

Docker-DCO-1.1-Signed-off-by: Guillaume J. Charmes <guillaume.charmes@docker.com> (github: creack)
Merge branch 'master' into add_freebsd_support

Conflicts:
	archive/archive.go
	archive/start_unsupported.go
Update vendor for kr/pty

Docker-DCO-1.1-Signed-off-by: Guillaume J. Charmes <guillaume.charmes@docker.com> (github: creack)
Update bsd specs

Docker-DCO-1.1-Signed-off-by: Guillaume J. Charmes <guillaume.charmes@docker.com> (github: creack)
Update vendor.sh with new kr/pty revision

Docker-DCO-1.1-Signed-off-by: Guillaume J. Charmes <guillaume@charmes.net> (github: creack)
Merge pull request #3985 from creack/add_freebsd_support

Add freebsd client support