codegen: Fix assignment to struct properties without accessors
codegen: Fix assignment to struct properties without accessors

Fixes bug 632137.

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