Add FlowAnalyzer.mark_unreachable
Add FlowAnalyzer.mark_unreachable

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