dix: add reference count of the resource to ResourceSizeRec

The ResourceSizeRec now contains the number of references to the
resource. For example a Pixmap knows this value and it can be useful
for determining the "weight" of the resource. Typically this value
is 1.

Reviewed-by: Rami Ylimäki <rami.ylimaki@vincit.fi>
Signed-off-by: Erkki Seppälä <erkki.seppala@vincit.fi>

include/resource.h

@@ -162,6 +162,8 @@ typedef struct {
     unsigned long resourceSize;
     /* Size attributed to pixmap references from the resource. */
     unsigned long pixmapRefSize;
+    /* Number of references to this resource; typically 1 */
+    unsigned long refCnt;
 } ResourceSizeRec, *ResourceSizePtr;
 
 typedef void (*SizeType)(pointer /*value*/,