Added three new helpers to be used by packages requiring GTK+ and

by pango itself.

To be able to run those helpers once the package has been stowned
properly, another variable available for templates has been added:
"postinstall_helpers".

This accepts a list of template helper names, e.g:

postinstall_helpers="gtk-update-gdkpixbufloaders.sh gtk-update-immodules.sh".

Also rather than setting extract_cmd itself in pkgfs.sh when
extract_sufx=".zip", set it in the helper itself.

--HG--
extra : convert_revision : 0f55c35f201daf6ff2e6d18cc808d0a34d8f4ddf

helper-templates/gtk-update-gdkpixbufloaders.sh

@@ -0,0 +1,17 @@
+#
+# This helper updates GTK's gdk-pixbug.loaders modules file every time
+# a template requests this process.
+#
+gtk_version="2.0"
+gdk_pixbuf_query_cmd=$PKGFS_MASTERDIR/bin/gdk-pixbuf-query-loaders
+gdk_pixbuf_db=$PKGFS_SYSCONFDIR/gtk-$gtk_version/gdk-pixbuf.loaders
+
+if [ -x $gdk_pixbuf_query_cmd -a -w $gdk_pixbuf_db ]; then
+	$gdk_pixbuf_query_cmd > $gdk_pixbuf_db
+	[ "$?" -eq 0 ] && \
+		echo "=> Updated GTK+ $(basename $gdk_pixbuf_db) modules file."
+fi
+
+unset gtk_version
+unset gdk_pixbuf_query_cmd
+unset gdk_pixbuf_dbfile