error_verbose yyoverflow conflict

[Christian Burger]

Hi!

Defining both %error_verbose and yyoverflow under bison v2.3
and compiling the generated code produces:

error: label 'yyexhaustedlab' used but not defined

Short program to reproduce the problem:

%{
#define yyoverflow handleoverflow
%}
%error_verbose
%%
start: ;

I realize yyoverflow is not exactly documented, but I find it
useful, and the problem is easy enough to fix. Thanks,

Chris