FYI: Declare YACC & YFLAGS precious in m4/bison.m4

[Derek Price]

This brings bison.m4 closer to what CVS is using.  Bruno approved the
YFLAGS change way back here:
<http://lists.gnu.org/archive/html/bug-autoconf/2004-05/msg00010.html>
and no one objected to my YACC correction in the following message.

2005-06-15  Derek Price  <address@hidden>

        * bison.m4: Declare YACC & YFLAGS precious.

Regards,

Derek

Index: m4/bison.m4
===================================================================
RCS file: /cvsroot/gnulib/gnulib/m4/bison.m4,v
retrieving revision 1.6
diff -u -p -r1.6 bison.m4
--- m4/bison.m4 2 Jun 2005 17:01:41 -0000       1.6
+++ m4/bison.m4 16 Jun 2005 12:53:29 -0000
@@ -9,5 +9,11 @@ AC_DEFUN([gl_BISON],
 [
   # getdate.y works with bison only.
   : ${YACC='bison -y'}
-  AC_SUBST(YACC)
+  AC_ARG_VAR(YACC,
+[The `Yet Another C Compiler' implementation to use.  Defaults to `bison -y'.
+Values other than `bison -y' will most likely break on most systems.])dnl
+  AC_ARG_VAR(YFLAGS,
+[YFLAGS contains the list arguments that will be passed by default to Bison.
+This script will default YFLAGS to the empty string to avoid a default value of
+`-d' given by some make applications.])dnl
 ])