Use VERSION symbol from automake for version number.

acconfig.h

@@ -0,0 +1,14 @@
+#ifndef CONFIG_H
+#define CONFIG_H
+
+@TOP@
+
+/* Name of package.  */
+#undef PACKAGE
+
+/* Version of package.  */
+#undef VERSION
+
+@BOTTOM@
+
+#endif  /* CONFIG_H */

configure.in

@@ -1,6 +1,6 @@
 dnl Process this file with autoconf to produce a configure script.
 AC_INIT(reduce.c)
-AM_INIT_AUTOMAKE(bison,1.25.90,nodef)
+AM_INIT_AUTOMAKE(bison,1.25.90)
 AM_CONFIG_HEADER(config.h:config.hin)
 
 dnl Checks for programs.
@@ -21,4 +21,4 @@ AC_C_CONST
 dnl Checks for library functions.
 AC_FUNC_ALLOCA
 
-AC_OUTPUT(Makefile version.c:version.cin)
+AC_OUTPUT(Makefile)

src/version.c

@@ -0,0 +1,3 @@
+#include <config.h>
+
+char *version_string = "GNU Bison version " VERSION "\n";

version.cin

@@ -1 +0,0 @@
-char *version_string = "GNU Bison version @VERSION@\n";