Keep the colleague's microbu-esp32c5 tree in this repository

obu-firmware builds against vanetza-idf from microbu-esp32c5/external, but
that tree was gitignored, so a clone of this repository could not build the
firmware it ships. It is now committed here as ordinary files in its own
folder, microbu-esp32c5/: the colleague's commit cf4b99f plus the V2X2MAP
bridge's signature verification (--trust) used on the bench. Nothing is
fetched from or pushed to the colleague's repository; this repository and
its remotes carry everything. The folder's own .gitignore keeps build output,
downloaded components and private key material out, as it did there; the
committed file set is identical to that repository's tracked files.

The ESP32-C5 is still flashed from obu-firmware/, which only takes
vanetza-idf from microbu-esp32c5/, so the two stay separate folders.
FLASHING.md says how to take a newer version of the colleague's tree (copy
it over the folder, rebuild, test, commit).

microbu-esp32c5/external/vanetza-idf/tools/socktap/autotalks.hpp

@@ -0,0 +1,69 @@
+#ifndef AUTOTALKS_HPP_
+#define AUTOTALKS_HPP_
+
+#include <cstddef>
+#include <memory>
+#include <vanetza/net/mac_address.hpp>
+#include <vanetza/access/data_request.hpp>
+#include <vanetza/net/chunk_packet.hpp>
+#include <vanetza/net/ethernet_header.hpp>
+#include <vanetza/net/cohesive_packet.hpp>
+#include "atlk/sdk.h"
+#include "atlk/v2x_service.h"
+#include "autotalks_link.hpp"
+
+namespace vanetza
+{
+namespace autotalks
+{
+
+/*
+ * Device initialization.
+ */
+int autotalks_device_init(void);
+
+/*
+ * Device deinitialization.
+ */
+int autotalks_device_deinit(void);
+
+/*
+ * Request sending in the API.
+ */
+atlk_rc_t autotalks_send(const void*, size_t, const v2x_send_params_t*, const atlk_wait_t*);
+
+/*
+ * Request reception in the API.
+ */
+atlk_rc_t autotalks_receive(void*, size_t*, v2x_receive_params_t*, const atlk_wait_t*);
+
+/*
+ * Convert MAC address to the Vanetza format
+ */
+vanetza::MacAddress num_to_mac(eui48_t);
+
+/*
+ * Convert Vanetza MAC format to the array
+ */
+eui48_t mac_to_num(vanetza::MacAddress);
+
+/*
+ * Create autotalks header and send the packet.
+ */
+void insert_autotalks_header_transmit(const vanetza::access::DataRequest&, std::unique_ptr<vanetza::ChunkPacket>&, uint8_t*, uint16_t);
+
+/*
+ * Parse information from received Autotalks packet.
+ */
+boost::optional<vanetza::EthernetHeader> strip_autotalks_rx_header(vanetza::CohesivePacket&, v2x_receive_params_t);
+
+/*
+ * Create a new thread for receiving data.
+ */
+void init_rx(AutotalksLink*);
+
+
+} // namespace autotalks
+} // namespace vanetza
+
+#endif /* AUTOTALKS_HPP_ */