Allow setnull=nan

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@31470 15284696-431f-4ddb-bdfa-cd5b030d7da7

raster/r.null/mask.c

@@ -65,5 +65,8 @@ int mask_match_d_interval (DCELL x, d_Interval *I)
     if (I->inf > 0)
 	return x >= I->high;
 
+    if (I->low != I->low && I->high != I->high)
+        return x != x;
+
     return x >= I->low && x <= I->high;
 }