girparser: support changing names of virtual methods without wrappers
girparser: support changing names of virtual methods without wrappers

Fixes bug 668991.

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