modernize bison rules * bootstrap.conf (gnulib_modules): Include bison in the list. * m4/acinclude.m4 (OCTAVE_PROG_BISON): Use gl_PROG_BISON to define BISON instead of AC_PROG_YACC to define YACC. Don't substitute WARN_YFLAGS. * libinterp/module.mk (%.cc %.h : %.yy): Assume we have bison, that it supports --defines=FILE and --output=FILE, and that we don't have to use ylwrap or work around weird y.tab.c and y.tab.h generated file names. * Makefile.am (AM_YFLAGS): Delete. (YACC): Define so that automake doesn't complain about seeing .yy source files without a definition of YACC in the Makefile. (AM_V_BISON, am__v_BISON_, am__v_BISON_0, am__v_BISON_1): New macros.

--- a/bootstrap.conf	Tue Sep 14 17:54:04 2021 +0900
+++ b/bootstrap.conf	Tue Sep 14 10:34:59 2021 -0400
@@ -29,6 +29,7 @@
 gnulib_modules="
   areadlink
   base64
+  bison
   canonicalize
   chdir
   clock-time