* src/muscle_tab.c (muscle_percent_define_flag_if): In order to

* src/muscle_tab.c (muscle_percent_define_flag_if): In order to
determine whether this function has already complained about an invalid
value for a %define boolean variable, don't check whether Bison has
ever examined the value.  As written, the check was a tautology.
Instead, record and check for this complaint using a separate muscle.