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/

nixos/modules/services/editors/emacs.xml

@@ -11,7 +11,7 @@
       Rodney Lorrimar @rvl
   -->
  <para>
-  <link xlink:href="http://www.gnu.org/software/emacs/">Emacs</link> is an
+  <link xlink:href="https://www.gnu.org/software/emacs/">Emacs</link> is an
   extensible, customizable, self-documenting real-time display editor — and
   more. At its core is an interpreter for Emacs Lisp, a dialect of the Lisp
   programming language with extensions to support text editing.