toolchain: add new debugging tool using magenta_debug

toolchain/mxdbg/client/packet.c

@@ -0,0 +1,15 @@
+#include "packet.h"
+
+#include <stdlib.h>
+
+struct packet *packet_create(size_t packet_size)
+{
+	size_t real_packet_size = sizeof(struct packet) + packet_size
+	                        - sizeof(struct mxdbg_packet);
+	return calloc(1, packet_size);
+}
+
+void packet_destroy(struct packet *packet)
+{
+	free(packet);
+}