busybox:
 * make FREETZ_BUSYBOX_CRYPTPW mandatory
 * fixes password of freetz' webif could not be changed because of missing mkpasswd (source:trunk/make/mod/files/root/usr/bin/modpasswd#L25)
 * mkpasswd is just an alias for cryptpw, selecting BUSYBOX_CRYPTPW causes both cryptpw and mkpasswd to be provided
 * refs #1786


git-svn-id: file:///var/svn/freetz/trunk@9888 149334a1-2f27-0410-a3b9-fc62619ac1e6