xbps-src: new target: bootstrap-update.

This target will update the bootstrap packages in masterdir
(if it was installed thru binary packages) to the most newer
version available in registered repositories.

xbps-src/shutils/chroot.sh.in

@@ -272,11 +272,7 @@ xbps_chroot_handler()
 {
 	local action="$1" pkg="$2" rv=0 arg
 
-	[ -z "$action" -o -z "$pkg" ] && return 1
-
-	[ "$action" != "configure" -a "$action" != "build" -a \
-	  "$action" != "install" -a "$action" != "chroot" -a \
-	  "$action" != "remove" ] && return 1
+	[ -z "$action" -a -z "$pkg" ] && return 1
 
 	if [ ! -f $XBPS_MASTERDIR/.xbps_perms_done ]; then
 		echo -n "==> Preparing chroot on $XBPS_MASTERDIR... "