Implementing adiabatic cooling as kpkt destruction choice

This change implements adiabatic cooling as a kpkt destruction choice so it works in macro atom mode.

This involves:
* Adding a destruction choice in kpkt(), with a probability proportional to the adiabatic_cooling in that cell, normalise by the total cooling
* this modifies istat to new definition P_ADIABATIC, which breaks loop in trans_phot()
* a new variable cooling_adiabatic is added to the macro pointer, and is lum_adiabatic/vol/ne
* this luminosity is reported by python.c in a loop- this will not sum correctly in parallel mode but I don't really want to add to the plasma pointer as its mainly diagnostic.