Add --exec-{send,receive}

adsbus/exec.h

@@ -0,0 +1,11 @@
+#pragma once
+
+#include <stdint.h>
+
+struct buf;
+struct peer;
+
+void exec_cleanup(void);
+typedef void (*exec_connection_handler)(int fd, void *, struct peer *);
+typedef void (*exec_get_hello)(struct buf **, void *);
+void exec_new(char *, exec_connection_handler, exec_get_hello, void *, uint32_t *);