Log Message:
all: migrate some SourceForge homepage URLs back from https to http

https://mail-index.netbsd.org/pkgsrc-changes/2020/01/18/msg205146.html

In the above commit, the homepage URLs were migrated from http to https,
assuming that SourceForge would use the same host names for both http and
https connections. This assumption was wrong. Their documentation at
https://sourceforge.net/p/forge/documentation/Custom%20VHOSTs/ states
that the https URLs use the domain sourceforge.io instead.

To make the homepages from the above commit reachable again, pkglint has
been extended to check for reachable homepages. This check is only
enabled when the --network command line option is given.

Each of the homepages that referred to https://$project.sourceforge.net
before was migrated to https://$project.sourceforge.io (27), and if that
was not reachable, to the fallback URL http://$project.sourceforge.net
(163).