additive kernel coeff can only be set via `env_state.additive_kernel_foefficient = ...`, not via ctor arg despite `call spec_file_read...` in PartMC code

[slayoo]

partmc/src/run_part.F90

Line 631 in 2341ef4

call spec_file_read_real(file, 'additive_kernel_coeff', &