Mapserver: enhancements of searching with GetFeatureInfo request

Currently when searching on layer with enabled scale dependent visibility and do not send BBOX, WIDTH and HEIGHT parameters, GetFeatureInfo doesn't return any features. So you have to compute values for these parameters to give mapserver info about scale. This may be probably a bug, because when you send BBOX parameter, it will be used only to calculate scale, not to restrict searching area.
This patch allows to search on whole layer (with scale dependent visibility) without passing BBOX, WIDTH and HEIGHT parameters, and also to use BBOX to restrict searching area.