Fix .begin and .end on async methods using generic types
Fix .begin and .end on async methods using generic types

Fixes bug 652763.

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