sane.ds: Return a 0 for MSG_QUERYSUPPORT even for capabilities we don't support.

dlls/sane.ds/capability.c

@@ -259,5 +259,10 @@ TW_UINT16 SANE_SaneCapability (pTW_CAPABILITY pCapability, TW_UINT16 action)
             break;
     }
 
+    /* Twain specifies that you should return a 0 in response to QUERYSUPPORT,
+     *   even if you don't formally support the capability */
+    if (twCC == TWCC_CAPUNSUPPORTED && action == MSG_QUERYSUPPORT)
+        twCC = set_onevalue(pCapability, 0, TWTY_INT32);
+
     return twCC;
 }