patch for gnu mig configure.ac Yacc.

[Chény , Yves-Gael]

Hello,
like in that message, 
https://lists.gnu.org/archive/html/bug-hurd/2013-02/msg00131.html
mig does not work with a non "bison"  version of yacc.

So, i propose this small patch for mig configure.ac to ensure that yacc version 
is provided by bison :

---------------

--- a/configure.ac
+++ b/configure.ac
@@ -24,7 +24,6 @@ m4_ifdef([AM_SILENT_RULES], [AM_SILENT_RULES([no])],
 dnl Checks for programs.
 AC_PROG_CC
 AC_PROG_CPP
-AC_PROG_YACC
 AM_PROG_LEX
 AC_PROG_AWK
 AC_PROG_INSTALL
@@ -36,6 +35,17 @@ dnl Checks for library functions.
 AC_FUNC_VPRINTF
 
 
+dnl check for bison for yacc
+AC_CHECK_PROG([YACC], yacc , [none])
+[if [ x"$YACC" == "x" ]; then]
+      AC_MSG_ERROR([could not find yacc provided by bison for the target you 
requested])
+[fi]
+
+AC_CHECK_PROG([BISON], bison, [none])
+[if [ x"$BISON" == "x" ]; then]
+      AC_MSG_ERROR([could not find bison are you sure yacc has been provided 
by bison ?])
+[fi]
+
 [if [ "$target" = "$host" ]; then
   TARGET_CC='${CC}'
 else]




----------------

i'm on irc for any questions, (hurdman_begin).
regards,
yves.