Changes

With wp3 now being set to a fixed-point boundary condition value
of 0 at the current thermodynamic level 2 (first t-lev above the
surface), it is not necessary to loop over level 2 within the code
for each wp3 term.

This commit is BIT_CHANGING, but only for the wp3 budget terms
(e.g. wp3_ta) in the zt output file at level k = 2. It doesn't change
the actual answer. All other variables are bit-for-bit identical.