abuild: include gtk-doc in the -doc subpackage

abuild

@@ -358,7 +358,7 @@ default_doc() {
 	depends="$depends_doc"
 	install="$install_doc"
 	local i
-	for i in doc man info html sgml licenses; do
+	for i in doc man info html sgml licenses gtk-doc; do
 		if [ -d "$pkgdir/usr/share/$i" ]; then
 			mkdir -p "$subpkgdir/usr/share"
 			mv "$pkgdir/usr/share/$i" "$subpkgdir/usr/share/"