In lalr1.cc we invoke it with the translated lookahead (yytoken), and
yacc.c uses yychar. I don't see why.
+** yysyntax_error
+The use of switch to select yyfmt in lalr1.cc seems simpler than
+what's done in yacc.c.
+
* Header guards
From Franc,ois: should we keep the directory part in the CPP guard?