The following commit turned out to be incomplete. This commit makes it
complete by removing client->lastDrawable/lastGC everywhere thus
fixing ArcticaProject/nx-libs#306 and #322

    commit e6f2f642
    Author: Mike Gabriel <mike.gabriel@das-netzwerkteam.de>
    Date:   Mon Jun 20 16:45:38 2016 +0200

        dix: remove caching of drawables and graphics contexts. The security checks simply bypass the cached values so they are unused.

         Backported from X.org:

         commit 9a183d7ba50e31afa133cc03aee7991517a283ea
         Author: Eamon Walsh <ewalsh@tycho.nsa.gov>
         Date:   Tue Aug 14 11:39:26 2007 -0400

            dix: remove caching of drawables and graphics contexts.  The security checks
            simply bypass the cached values so they are unused.

         Backport to nx-libs: Mike Gabriel <mike.gabriel@das-netzwerkteam.de>