gidlparser: Support abstract metadata for properties
gidlparser: Support abstract metadata for properties

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