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/misc/keepassx/2.0.nix

@@ -1,4 +1,4 @@
-{ stdenv, fetchurl, cmake, libgcrypt, qt4, xlibs, ... }:
+{ stdenv, fetchurl, cmake, libgcrypt, qt4, xorg, ... }:
 
 stdenv.mkDerivation {
   name = "keepassx2-2.0beta2";
@@ -7,7 +7,7 @@ stdenv.mkDerivation {
     sha256 = "0ljf9ws3wh62zd0gyb0vk2qw6pqsmxrlybrfs5mqahf44q92ca2q";
   };
 
-  buildInputs = [ cmake libgcrypt qt4 xlibs.libXtst ];
+  buildInputs = [ cmake libgcrypt qt4 xorg.libXtst ];
 
   meta = {
     description = "Qt password manager compatible with its Win32 and Pocket PC versions";