max_BD_range: Adjusting BD range size if negative.
Description
If BD (buoyant density) range size is negative,
use BD_to_set value to set new BD_max. The BD_to_set
determines the BD_max
if BD range is negative
Usage
max_BD_range(BD_range, BD_min, BD_max, BD_to_set)
Arguments
BD_to_set
Value added to BD_min to set new BD_max