scripts/functions: only use one download program

Currently, we use either wget or curl, whichever is installed.
In case both are installed, both are used. This means that it
takes a while trying all extensions.

Remove use of wget, and use only curl.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

This is NOT the official version of dialog.  This version has been

significantly modified from the original.  It is for use by the Linux

kernel configuration script.  Please do not bother Savio Lam with 

questions about this program.