Treewide: use HTTPS on GNU Savannah domains

HTTP -> HTTPS for:
- http://savannah.gnu.org/
- http://git.savannah.gnu.org/
- http://download.savannah.gnu.org/
- http://svn.savannah.gnu.org/

pkgs/development/libraries/gnutls-kdh/generic.nix

@@ -47,7 +47,7 @@ stdenv.mkDerivation {
     [ "--enable-guile" "--with-guile-site-dir=\${out}/share/guile/site" ];
 
   # Build of the Guile bindings is not parallel-safe.  See
-  # <http://git.savannah.gnu.org/cgit/gnutls.git/commit/?id=330995a920037b6030ec0282b51dde3f8b493cad>
+  # <https://github.com/arpa2/gnutls-kdh/commit/330995a920037b6030ec0282b51dde3f8b493cad>
   # for the actual fix.  Also an apparent race in the generation of
   # systemkey-args.h.
   enableParallelBuilding = false;