Added a preprocessor if condition around the definition of
"Write_RefRules" because it is used in such an environment.
````
static INT Write_RefRules (MULTIGRID *theMG, INT *RefRuleOffset, INT MarkKey)
{
  ...
}
````

Furthermore there is a comment adressing the only use of "Write_RefRules".

````
/* TODO (HRR 971209): drop old call of Write_RefRules */
  #if EXTRACT_RULES
if (NEW_Write_RefRules(theMG,rr_rule_offsets,MarkKey,&rr_rules)) REP_ERR_RETURN(1)       ;
      #else
if (Write_RefRules(theMG,rr_rule_offsets,MarkKey)) REP_ERR_RETURN(1);
      #endif
````
But i am not sure whether "Write_RefRules" is still needed.