Vernalization subroutine should probably have some dtime dependence

I noticed this when investigating the possible impacts of #1626 : It looks like the vernalization subroutine in CNPhenologyMod accumulates some variables each time it's called, but there is no multiplication by dtime. I haven't come to fully understand what's going on in that subroutine, but it seems suspicious that there is no dtime multiplier: If this subroutine was called twice as often (due to a decrease in time steps from 30 to 15 min), would vernalization accumulation happen twice as fast?

@slevisconsulting is this something you're familiar with?