scripts: add possibility to not override default connection timeout

Allow '-1' to be specified as CONNECTION_TIMEOUT to disable the use
of the connection timeout for wget.

Signed-off-by: Cody P Schafer <dev@codyps.com>
Message-Id: <cb33f8c2cbaf802d4f04.1399687632@localhost>
Patchwork-Id: 347582

 #!/bin/sh

 set -e

 printf "Running autoconf...\n"

 autoconf -Wall --force

 printf "Done. You may now run:\n    ./configure\n"