Move libcw setup to the only renderer requiring it (XAA).

Additionally, protect libcw setup behind checks for Render, to avoid
segfaulting if Render isn't available (xnest).

The previous setup was an ABI-preserving dance, which is better nuked now.
Now, anything that needs libcw must explicitly initialize it, and
miDisableCompositeWrapper (previously only called by EXA and presumably binary
drivers) is gone.

miext/damage/damage.c

@@ -1831,16 +1831,6 @@ DamageSetup (ScreenPtr pScreen)
     if (!pScrPriv)
 	return FALSE;
 
-#ifdef COMPOSITE
-    /* This is a kludge to ensure wrapping order with the composite wrapper.
-     * If it's done from compinit.c, then DamageSetup may be called before the
-     * extension init phase, so that cw will be higher in the wrapping chain and
-     * rewrite drawables before damage gets to it, causing confusion.
-     */
-    if (!noCompositeExtension)
-	miInitializeCompositeWrapper (pScreen);
-#endif
-	
     pScrPriv->internalLevel = 0;
     pScrPriv->pScreenDamage = 0;