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/libxmi/default.nix

@@ -13,7 +13,7 @@ stdenv.mkDerivation {
 
   meta = {
     description = "Library for rasterizing 2-D vector graphics";
-    homepage = http://www.gnu.org/software/libxmi/;
+    homepage = https://www.gnu.org/software/libxmi/;
     license = stdenv.lib.licenses.gpl2Plus;
     platforms = stdenv.lib.platforms.gnu ++ stdenv.lib.platforms.linux;  # arbitrary choice
     maintainers = [ ];