autoconf: check for wget and ftp

autoconf: check for wget and ftp

Some OSes don't come with wget by default, so ftp should be choosen
on those. Add an autoconf check to check for wget and ftp, and
replace the usage of hardcoded wget in tools.

[ Stubdom builds still use wget unconditionally. -iwj ]

Signed-off-by: Christoph Egger <Christoph.Egger@amd.com>
Signed-off-by: Roger Pau Monne <roger.pau@citrix.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
Committed-by: Ian Jackson <ian.jackson@eu.citrix.com>