conf: add tool to print regex name/regex pairs as re2r input

this is currently not included in the build system and needs to be
compiled by hand.

src/conf_regex_print.c

@@ -0,0 +1,14 @@
+/* this is a tool to print regexname regex pairs as input for re2r.
+   compile with gcc -I. src/conf_regex_print.c
+ */
+
+#include "config.h"
+
+#include <stdio.h>
+
+#define STDCONF(A, B, C) printf("%s %s\n", #A, B)
+
+int main() {
+#include "conf_regex.h"
+;
+}