Add CONFIG_ARGS Makefile variable (saves the arguments passed
to configure).
diff --git a/configure.in b/configure.in
index 5c12aa4..75b9d32 100644
--- a/configure.in
+++ b/configure.in
@@ -8,6 +8,10 @@
 AC_SUBST(VERSION)
 VERSION=2.1
 
+# Arguments passed to configure.
+AC_SUBST(CONFIG_ARGS)
+CONFIG_ARGS="$ac_configure_args"
+
 # NEXTSTEP|MacOSX|Darwin stuff
 if test -f /usr/lib/NextStep/software_version -o -f /System/Library/CoreServices/software_version ; then