x11: Add XImage bindings
x11: Add XImage bindings

Fixes bug 681961.

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