Fix code generation for destroy_notify calls for delegate targets
Fix code generation for destroy_notify calls for delegate targets

Fixes bug 615440.

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