[gnumeric] Configure: fail if bison/flex isn't found.

[Morten Welinder <mortenw src gnome org>]

commit abdc50efbbe66e6f9a4c51e51d1e4512c182c710
Author: Morten Welinder <terra gnome org>
Date:   Mon Feb 1 16:42:12 2016 -0500

    Configure: fail if bison/flex isn't found.

 ChangeLog    |    5 +++++
 NEWS         |    2 ++
 configure.ac |    8 ++++++++
 3 files changed, 15 insertions(+), 0 deletions(-)
---
diff --git a/ChangeLog b/ChangeLog
index 41dcfd6..edfd717 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2016-02-01  Morten Welinder  <terra gnome org>
+
+       * configure.ac (yacc, lex): Fail if the required program isn't
+       found.
+
 2016-01-31  Morten Welinder  <terra gnome org>
 
        * src/sf-gamma.c (igamma_upper_cf): Extract generic code for
diff --git a/NEWS b/NEWS
index cc13cde..cb11dd3 100644
--- a/NEWS
+++ b/NEWS
@@ -26,6 +26,8 @@ Morten:
        * Improve BETA accuracy.
        * Fix problem with database functions.  [#761305]
        * Fix font problem for ssconvert to pdf.  [#761296]
+       * Fix bison check.  [#761398]
+
 
 --------------------------------------------------------------------------
 Gnumeric 1.12.26
diff --git a/configure.ac b/configure.ac
index c9939ce..8959c7a 100644
--- a/configure.ac
+++ b/configure.ac
@@ -85,7 +85,15 @@ if test "$ac_cv_prog_cc_c99" = no; then
 fi
 
 AC_PROG_YACC
+if test "x$ac_cv_prog_YACC" = x; then
+       AC_MSG_ERROR([*** bison or equivalent is required])
+fi
+
 AM_PROG_LEX
+if test "x$ac_cv_prog_LEX" = x; then
+       AC_MSG_ERROR([*** flex or equivalent is required])
+fi
+
 AC_PROG_LN_S
 AC_HEADER_STDC