wget:
 * make it possible to have both GNU and busybox versions of wget in image: call {{{wget-gnu}}} if you need GNU Wget (e.g. because of SSL support) or just {{{wget}}} if it doesn't matter for you which version to use
 * provide an option ensuring that wget is available even if the medium containing external'ed files is not plugged in
 * this restores the behavior which were possible before r11207, it also fixes the problems like [http://www.telefonsparbuch.de/tmpl/calc/telephone/lcr/info/fritzbox_lcrupdater_download.htm LCR-Updateri] doesn't work if external medium is not plugged in
 * refs #2237


git-svn-id: file:///var/svn/freetz/trunk@11633 149334a1-2f27-0410-a3b9-fc62619ac1e6