SAVSNP ( nchars, filnam, histfl, ifail )
========================================

  Make a snapshot

Receives:
  KI_int_nchars            *nchars         --- number of characters in filename
  KI_chr_filename           filnam[nchars] --- filename for snapshot
  int                      *histfl         --- unused: should be zero

Returns:
  KI_cod_error             *ifail          --- error code

Specific errors:
  KI_bad_text_conversion    invalid value for text output
  KI_file_already_exists    snapshot file of the given name already exists
  KI_schema_access_error    error opening, closing or writing the schema file
  KI_file_access_error      error writing or closing snapshot file
  KI_cant_open_file         cannot open snapshot file
  KI_bad_filename           invalid filename

Description:
  Saves the state of tag-memory in a snapshot file, so that it can later be
  restored via a call to GETSNP. Rollback information is not saved.

  Note that a snapshot file can only be restored by the same version of the
  modeller which generated it.