Align gtk templates to new gtk+/glib api
Align gtk templates to new gtk+/glib api

Based on patch by ebassi.

flobrosch/vala-fixes,spidermonkdust/vala,frida/vala,frida/vala,flobrosch/vala-fixes,flobrosch/vala-fixes,GNOME/vala,frida/vala,rvu95/vala,rvu95/vala,frida/vala,spidermonkdust/vala,Distrotech/vala,GNOME/vala,xdave/pvala,spidermonkdust/vala,GNOME/vala,rvu95/vala,Distrotech/vala,frida/vala,Distrotech/vala,GNOME/vala