/**
 * - is_valid_z_level
 *
 * Checks if source_loc and checking_loc is both on the station, or on the same z level.
 * This is because the station's several levels aren't considered the same z, so multi-z stations need this special case.
 *
 * Args:
 * source_loc - turf of the source we're comparing.
 * checking_loc - turf we are comparing to source_loc.
 *
 * returns TRUE if connection is valid, FALSE otherwise.
 */
/proc/is_valid_z_level(turf/source_loc, turf/checking_loc)
	// if we're both on "station", regardless of multi-z, we'll pass by.
	if(is_station_level(source_loc.z) && is_station_level(checking_loc.z))
		return TRUE
	if(source_loc.z == checking_loc.z)
		return TRUE
	return FALSE