dix: add deletable field to PropertyRec

Preparational step for later using this struct for XI.

Signed-off-by: Enrico Weigelt, metux IT consult <info@metux.net>

include/propertyst.h

@@ -61,6 +61,7 @@ typedef struct _Property {
     ATOM propertyName;
     PropertyValueRec value;
     PrivateRec *devPrivates;
+    Bool deletable;
 } PropertyRec;
 
 #endif                          /* PROPERTYSTRUCT_H */