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/data/documentation/zeal/default.nix

@@ -1,4 +1,4 @@
-{ stdenv, fetchFromGitHub, pkgconfig, qt5, libarchive, xlibs }:
+{ stdenv, fetchFromGitHub, pkgconfig, qt5, libarchive, xorg }:
 
 stdenv.mkDerivation rec {
   version = "0.1.1";
@@ -12,7 +12,7 @@ stdenv.mkDerivation rec {
   };
 
   buildInputs = [
-    xlibs.xcbutilkeysyms pkgconfig qt5.base qt5.webkit qt5.imageformats libarchive
+    xorg.xcbutilkeysyms pkgconfig qt5.base qt5.webkit qt5.imageformats libarchive
   ];
 
   configurePhase = ''