configs/releng/packages.x86_64: add squashfs-tools and udftools

- squashfs-tools can be used for system backup. https://wiki.archlinux.org/index.php/Full_system_backup_with_SquashFS
- udftools is needed to format UDF file systems.

configs/releng/packages.x86_64

@@ -76,6 +76,7 @@ rxvt-unicode-terminfo
 sdparm
 sg3_utils
 smartmontools
+squashfs-tools
 sudo
 syslinux
 systemd-resolvconf
@@ -83,6 +84,7 @@ tcpdump
 terminus-font
 termite-terminfo
 testdisk
+udftools
 usb_modeswitch
 usbutils
 vim