Config.in: update default CPAN mirror to https, update mirrors URL

The http site automatically redirects to the https variant, so let's
just use that as the default.

The mirror list URL http://search.cpan.org/mirror seems outdated
(re-directed to https://metacpan.org/mirrors aka 'Not Found - The
resource you requested could not be found.').

The closest matching URLs we found were:

  https://www.cpan.org/SITES.html
  http://mirrors.cpan.org/map.html
  http://mirrors.cpan.org/

That last one has all the list, so we use that; the second is a world
map, so we also include it.

Sadly, neither of the mirrors list (table or map) are served as https;
they are only available as http...

Signed-off-by: Peter Seiderer <ps.report@gmx.net>
[yann.morin.1998@free.fr:
  - add a little blurb to explain http->https redirect
  - update the mirror list URL, and...
  - extend commit message with original explanations from Peter, and..
  - notice that they are not served via https...
]
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
(cherry picked from commit add21fd600b2db4dbb930e2e62b9fbb1b72cceb9)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

Config.in

@@ -285,14 +285,15 @@ config BR2_LUAROCKS_MIRROR
 
 config BR2_CPAN_MIRROR
 	string "CPAN mirror (Perl packages)"
-	default "http://cpan.metacpan.org"
+	default "https://cpan.metacpan.org"
 	help
 	  CPAN (Comprehensive Perl Archive Network) is a repository of
 	  Perl packages. It has multiple software mirrors scattered
 	  around the world. This option allows you to select a mirror.
 
 	  The list of mirrors is available at:
-	  http://search.cpan.org/mirror
+	  http://mirrors.cpan.org/          (tabular)
+	  http://mirrors.cpan.org/map.html  (clickable world map)
 
 endif