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FLASHING.md says how to take a newer version of the colleague's tree (copy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/vanetza/asn1/support/RELATIVE-OID_print.c

@@ -0,0 +1,28 @@
+/*
+ * Copyright (c) 2017 Lev Walkin <vlm@lionet.info>.
+ * All rights reserved.
+ * Redistribution and modifications are permitted subject to BSD license.
+ */
+#include "asn_internal.h"
+#include "RELATIVE-OID.h"
+
+int
+RELATIVE_OID_print(const asn_TYPE_descriptor_t *td, const void *sptr,
+                   int ilevel, asn_app_consume_bytes_f *cb, void *app_key) {
+    const RELATIVE_OID_t *st = (const RELATIVE_OID_t *)sptr;
+
+    (void)td;  /* Unused argument */
+    (void)ilevel;  /* Unused argument */
+
+    if(!st || !st->buf)
+        return (cb("<absent>", 8, app_key) < 0) ? -1 : 0;
+
+    /* Dump preamble */
+    if(cb("{ ", 2, app_key) < 0)
+        return -1;
+
+    if(RELATIVE_OID__dump_body(st, cb, app_key) < 0)
+        return -1;
+
+    return (cb(" }", 2, app_key) < 0) ? -1 : 0;
+}