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FLASHING.md says how to take a newer version of the colleague's tree (copy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

@@ -0,0 +1,58 @@
+/*-
+ * Copyright (c) 2003, 2004 Lev Walkin <vlm@lionet.info>. All rights reserved.
+ * Redistribution and modifications are permitted subject to BSD license.
+ */
+#include "asn_internal.h"
+#include <stdio.h>
+#include <errno.h>
+
+/*
+ * The JER encoder of any type. May be invoked by the application.
+ */
+asn_enc_rval_t
+jer_encode(const asn_TYPE_descriptor_t *td, const void *sptr,
+           enum jer_encoder_flags_e jer_flags,
+           asn_app_consume_bytes_f *cb, void *app_key) {
+    asn_enc_rval_t er = {0, 0, 0};
+	asn_enc_rval_t tmper;
+
+	if(!td || !sptr) goto cb_failed;
+
+	tmper = td->op->jer_encoder(td, 0, sptr, 0, jer_flags, cb, app_key);
+	if(tmper.encoded == -1) return tmper;
+	er.encoded += tmper.encoded;
+
+	ASN__ENCODED_OK(er);
+cb_failed:
+	ASN__ENCODE_FAILED;
+}
+
+/*
+ * This is a helper function for jer_fprint, which directs all incoming data
+ * into the provided file descriptor.
+ */
+static int
+jer__print2fp(const void *buffer, size_t size, void *app_key) {
+	FILE *stream = (FILE *)app_key;
+
+	if(fwrite(buffer, 1, size, stream) != size)
+		return -1;
+
+	return 0;
+}
+
+int
+jer_fprint(FILE *stream, const asn_TYPE_descriptor_t *td, const void *sptr) {
+	asn_enc_rval_t er = {0,0,0};
+
+	if(!stream) stream = stdout;
+	if(!td || !sptr)
+		return -1;
+
+	er = jer_encode(td, sptr, JER_F, jer__print2fp, stream);
+	if(er.encoded == -1)
+		return -1;
+
+	return fflush(stream);
+}
+