exa: drop cw.h inclusion

this doesn't seem to be needed, at least I can't see any warning without it.

I'd like to build EXA into a driver and cw.h isn't exported

exa/exa.c

@@ -36,7 +36,6 @@
 
 #include "exa_priv.h"
 #include "exa.h"
-#include "cw.h"
 
 static int exaScreenPrivateKeyIndex;
 DevPrivateKey exaScreenPrivateKey = &exaScreenPrivateKeyIndex;

exa/exa_accel.c

@@ -34,7 +34,6 @@
 #include <X11/fonts/fontstruct.h>
 #include "dixfontstr.h"
 #include "exa.h"
-#include "cw.h"
 
 static void
 exaFillSpans(DrawablePtr pDrawable, GCPtr pGC, int n,

exa/exa_migration.c

@@ -34,7 +34,6 @@
 
 #include "exa_priv.h"
 #include "exa.h"
-#include "cw.h"
 
 #if DEBUG_MIGRATE
 #define DBG_MIGRATE(a) ErrorF a