posix: add tzset(3) and assorted constants
posix: add tzset(3) and assorted constants

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