posix.vapi: add missing getopt part
posix.vapi: add missing getopt part

Fixes bug 694508.

Distrotech/vala,frida/vala,rvu95/vala,rvu95/vala,GNOME/vala,spidermonkdust/vala,spidermonkdust/vala,xdave/pvala,playya/vala,playya/vala,flobrosch/vala-fixes,GNOME/vala,spidermonkdust/vala,rvu95/vala,Distrotech/vala,frida/vala,Distrotech/vala,frida/vala,GNOME/vala,flobrosch/vala-fixes,frida/vala,frida/vala,flobrosch/vala-fixes,GNOME/vala,playya/vala