posix.vapi: add nice(2)
posix.vapi: add nice(2)

Signed-off-by: Michael 'Mickey' Lauer <1aa25ead3880825480b6c0197552d90eb5d48d23@vanille-media.de>

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