Treewide: use HTTPS on GNU domains

HTTP -> HTTPS for :
- http://gnu.org/
- http://www.gnu.org/
- http://elpa.gnu.org/
- http://lists.gnu.org/
- http://gcc.gnu.org/
- http://ftp.gnu.org/ (except in fetchurl mirrors)
- http://bugs.gnu.org/

pkgs/development/libraries/gcc/libstdc++/5.nix

@@ -108,7 +108,7 @@ stdenv.mkDerivation rec {
   '';
 
   meta = with stdenv.lib; {
-    homepage = http://gcc.gnu.org/;
+    homepage = https://gcc.gnu.org/;
     license = licenses.lgpl3Plus;
     description = "GNU Compiler Collection, version ${version} -- C++ standard library";
     platforms = platforms.linux;