codegen: Fix handling of leaked values in transform_value
codegen: Fix handling of leaked values in transform_value

Fixes bug 654619.

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