Fix some issues reported by deronj:

- Hopefully fix a crash in compCheckRedirect on unrealizing windows.
- Remove an extern that doesn't point at anything.

composite/compint.h

@@ -75,8 +75,6 @@ typedef struct _CompSubwindows {
     CompClientWindowPtr	    clients;
 } CompSubwindowsRec, *CompSubwindowsPtr;
 
-extern int  CompPixmapPrivateIndex;
-
 #define NUM_COMP_ALTERNATE_VISUALS  2
 
 typedef struct _CompScreen {

composite/compwindow.c

@@ -103,7 +103,10 @@ Bool
 compCheckRedirect (WindowPtr pWin)
 {
     CompWindowPtr   cw = GetCompWindow (pWin);
-    Bool	    should = pWin->viewable && (cw != NULL);
+    Bool	    should;
+
+    should = pWin->realized && (pWin->drawable.class != InputOnly) &&
+	     (cw != NULL);
     
     if (should != pWin->redirectDraw)
     {