Comet parameter: variable_C_terminus_distance

Example:
variable_C_terminus_distance = -1   Applied to all peptides
variable_C_terminus_distance = 0     Applied only to peptides containing protein's c-terminus
variable_C_terminus_distance = 3     Applied on any peptide who's c-terminus is one of last 4 residues (c-term & next 3)
variable_C_terminus_distance = 20   Applied on any peptide who's c-terminus is one of last 21 residues (c-term & next 20)