Comment out 'optional_string' which was defined but not used, causing YACC on a number of platforms to die.
Comment out 'optional_string' which was defined but not used, causing YACC
on a number of platforms to die.

pecharmin/bind9,pecharmin/bind9,each/bind9-collab,pecharmin/bind9,each/bind9-collab,pecharmin/bind9,each/bind9-collab,each/bind9-collab,each/bind9-collab,each/bind9-collab,pecharmin/bind9,pecharmin/bind9