GROMACS

While fixing #2077, Berk proposed adding one-off code to write the final line of

ERROR 3 [file ddt2.prm, line 23]:
  Encountered a second block of parameters for dihedral type 9 for the same
  atoms, with either different parameters and/or the first block has
  multiple lines. This is not supported.

  line: CG2R51   CG2R51    CG321    CG321     9     0.000000     0.000000     3

This would be better done centrally, e.g. by passing the line to set_warning_line(), so that it is available and can be appended to messages for the convenience of users (and people helping with trouble-shooting on gmx-users).