(new) preprocess could set the 'source' line in the generated files

[nancycollins]

(low priority) while i was testing something i got an error that said it was from DEFAULT_obs_kind_mod.F90. what's really compiled into the executable is the output of preprocess, usually obs_kind_mod.f90, but that filename is changeable by namelist. the preprocess program could generate a source character string using the output file namelist string, for both the obs_kind and obs_def files, so in messages it would print the actual source module containing the generated code.