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FLASHING.md says how to take a newer version of the colleague's tree (copy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/NativeInteger_print.c

@@ -0,0 +1,43 @@
+/*
+ * 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 "NativeInteger.h"
+
+/*
+ * INTEGER specific human-readable output.
+ */
+int
+NativeInteger_print(const asn_TYPE_descriptor_t *td, const void *sptr,
+                    int ilevel, asn_app_consume_bytes_f *cb, void *app_key) {
+    const asn_INTEGER_specifics_t *specs =
+        (const asn_INTEGER_specifics_t *)td->specifics;
+    const long *native = (const long *)sptr;
+    char scratch[32];  /* Enough for 64-bit int */
+    int ret;
+
+    (void)td;      /* Unused argument */
+    (void)ilevel;  /* Unused argument */
+
+    if(native) {
+        long value = *native;
+        ret = snprintf(scratch, sizeof(scratch),
+                       (specs && specs->field_unsigned) ? "%lu" : "%ld", value);
+        assert(ret > 0 && (size_t)ret < sizeof(scratch));
+        if(cb(scratch, ret, app_key) < 0) return -1;
+        if(specs && (value >= 0 || !specs->field_unsigned)) {
+            const asn_INTEGER_enum_map_t *el =
+                INTEGER_map_value2enum(specs, value);
+            if(el) {
+                if(cb(" (", 2, app_key) < 0) return -1;
+                if(cb(el->enum_name, el->enum_len, app_key) < 0) return -1;
+                if(cb(")", 1, app_key) < 0) return -1;
+            }
+        }
+        return 0;
+    } else {
+        return (cb("<absent>", 8, app_key) < 0) ? -1 : 0;
+    }
+}