rcutorture: Replace HTTP links with HTTPS ones

Rationale:
Reduces attack surface on kernel devs opening the links for MITM
as HTTPS traffic is much harder to manipulate.

Deterministic algorithm:
For each file:
  If not .svg:
    For each line:
      If doesn't contain `\bxmlns\b`:
        For each link, `\bhttp://[^# \t\r\n]*(?:\w|/)`:
	  If neither `\bgnu\.org/license`, nor `\bmozilla\.org/MPL\b`:
            If both the HTTP and HTTPS versions
            return 200 OK and serve the same content:
              Replace HTTP with HTTPS.
Signed-off-by: Alexander A. Klimov <grandmaster@al2klimov.de>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

tools/testing/selftests/rcutorture/doc/rcu-test-image.txt

@@ -36,7 +36,7 @@ References:
 	https://help.ubuntu.com/community/JeOSVMBuilder
 	http://wiki.libvirt.org/page/UbuntuKVMWalkthrough
 	http://www.moe.co.uk/2011/01/07/pci_add_option_rom-failed-to-find-romfile-pxe-rtl8139-bin/ -- "apt-get install kvm-pxe"
-	http://www.landley.net/writing/rootfs-howto.html
-	http://en.wikipedia.org/wiki/Initrd
-	http://en.wikipedia.org/wiki/Cpio
+	https://www.landley.net/writing/rootfs-howto.html
+	https://en.wikipedia.org/wiki/Initrd
+	https://en.wikipedia.org/wiki/Cpio
 	http://wiki.libvirt.org/page/UbuntuKVMWalkthrough