Change `setaux` subroutine interface to include aux copy mask array

This PR changes the setaux function interface to also include an `integer(kind=1)` array called `aux_copy_mask` that will eventually hold a masking array so that setaux can know which cells to fill and which not to in order to reduce a possibly expensive function evaluation.  Currently this functionality has not been fully implemented but will be added in version 5.1 (hopefully).