xlibs: replace occurrences by xorg

This seems to have been confusing people, using both xlibs and xorg, etc.
- Avoided renaming local (and different) xlibs binding in gcc*.
- Fixed cases where both xorg and xlibs were used.
Hopefully everything still works as before.

pkgs/applications/editors/sublime/default.nix

@@ -1,6 +1,6 @@
-{ fetchurl, stdenv, glib, xlibs, cairo, gtk}:
+{ fetchurl, stdenv, glib, xorg, cairo, gtk}:
 let
-  libPath = stdenv.lib.makeLibraryPath [glib xlibs.libX11 gtk cairo];
+  libPath = stdenv.lib.makeLibraryPath [glib xorg.libX11 gtk cairo];
 in
 assert stdenv.system == "i686-linux" || stdenv.system == "x86_64-linux";