Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

MFC r264840: Implement GEOM based media device classification.

MFC revisions 255908, 255925, and 255925:

SVN r255908:
Fix a bug in HTTP checking/fetching. Add Main Site to HTTP menu. Add new
example script browse_packages_http.sh and move existing example script
browse_packages.sh -> browse_packages_ftp.sh

SVN r255925:
Remove the is (Iceland) mirror per mail from the admins.

SVN r255925:
Remove ftp5.se.f.o, as per request to -hubs@

MFC r255340:

Long URLs don't always appear even with autosizing and other tricks. So,
add some whitespace to put the URL on a line by itself, maximizing view.

MFC r255341:

Remove unnecessary mediaClose (FTP operations are done with either ftp(1)
or fetch(1), neither of which are stateful, compared to how sysinstall(8)
did FTP operations, maintaining an open session until mediaClose).

MFC bsdconfig(8) and sysrc(8) from HEAD. (shazam!)