posix: Add pseudo terminal functions
posix: Add pseudo terminal functions

Add posix_openpt(3), grantpt(3), and unlockpt(3) bindings.

Signed-off-by: Michael 'Mickey' Lauer <94b327e99abc3aa97363840c77d9a097d094d304@vanille-media.de>

GNOME/vala,themiwi/vala,Distrotech/vala,spidermonkdust/vala,spidermonkdust/vala,frida/vala,spidermonkdust/vala,playya/vala,lovebug356/vala,xdave/pvala,kamanashisroy/aroop,Jc2k/vala,kamanashisroy/aroop,themiwi/vala,Jc2k/vala,severinh/vala,GNOME/vala,tjol/vala-tjol,flobrosch/vala-fixes,GNOME/vala,jessevdk/vala,phako/vala,frida/vala,Distrotech/vala,lovebug356/vala,flobrosch/vala-fixes,playya/vala,severinh/vala,kamanashisroy/aroop,rvu95/vala,frida/vala,flobrosch/vala-fixes,rvu95/vala,frida/vala,tjol/vala-tjol,severinh/vala,Distrotech/vala,themiwi/vala,GNOME/vala,playya/vala,phako/vala,jessevdk/vala,jessevdk/vala,rvu95/vala,tjol/vala-tjol,frida/vala