configure: Require a new enough flex version.
Wine needs a newer flex version than the prediluvian 2.5.4a.
diff --git a/configure b/configure
index 3e5f93e..e0ae0d2 100755
--- a/configure
+++ b/configure
@@ -4214,6 +4214,23 @@
then
as_fn_error "no suitable flex found. Please install the 'flex' package." "$LINENO" 5
fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether flex is recent enough" >&5
+$as_echo_n "checking whether flex is recent enough... " >&6; }
+cat >conftest.l <<EOF
+%top{
+#include "prediluvian.h"
+}
+%%
+EOF
+if $FLEX -t conftest.l >/dev/null 2>&1
+then
+ { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
+$as_echo "yes" >&6; }
+else
+ { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+ as_fn_error "Your flex version is too old. Please install flex version 2.5.33 or newer." "$LINENO" 5
+fi
for ac_prog in bison
do
