This function is called by fprintf_unit to write the following fields:
ActFunc,TransFunc,DerTransFunc,DerDerTransFunc,TransFuncPar1,TransFuncPar2 and TransFuncPar3. Note that the ActFunc and the various
TransFunc fields can be USERDEFINED or NULL in the file,
but that the check_all_network
function which is called by fscanf_network will return an error in that case.
See NET-IO-format for the layout of this part.
NOTE
The function uses the get_act_func_name and get_trans_func_name
functions to translate from function pointers to ASCII.
The parameters (TransFuncPar1,TransFuncPar2 and TransFuncPar3) are only
written when appropriate. Currently, only the TransParTanH function
(the parametric hyperbolic tangent transfer function) uses two parameters.
