gdl-3.0: update to 3.7.3
gdl-3.0: update to 3.7.3

Fixes bug 693127.

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