iOS 3/4 compatible locationServices check

gistfile1.m

BOOL locationAccessAllowed = NO;
if( [CLLocationManager instancesRespondToSelector:@selector(locationServicesEnabled)] )
{
    // iOS 3.x and earlier
    locationAccessAllowed = locationManager.locationServicesEnabled ;
}
else if( [CLLocationManager respondsToSelector:@selector(locationServicesEnabled)] )
{
    // iOS 4.x
    locationAccessAllowed = [CLLocationManager locationServicesEnabled] ;
}