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FLASHING.md says how to take a newer version of the colleague's tree (copy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

@@ -0,0 +1,70 @@
+/*
+ * Copyright (c) 2017 Lev Walkin <vlm@lionet.info>. All rights reserved.
+ * Redistribution and modifications are permitted subject to BSD license.
+ */
+#ifndef	OER_ENCODER_H
+#define	OER_ENCODER_H
+
+#include "asn_application.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+struct asn_TYPE_descriptor_s;	/* Forward declaration */
+
+/*
+ * The Octet Encoding Rules (OER, X.696 08/2015) encoder for any type.
+ * This function may be invoked directly by the application.
+ * Produces CANONICAL-OER output compatible with CANONICAL-OER
+ * and BASIC-OER decoders.
+ */
+asn_enc_rval_t oer_encode(const struct asn_TYPE_descriptor_s *type_descriptor,
+                          const void *struct_ptr, /* Structure to be encoded */
+                          asn_app_consume_bytes_f *consume_bytes_cb,
+                          void *app_key /* Arbitrary callback argument */
+);
+
+/* A variant of oer_encode() which encodes data into the pre-allocated buffer */
+asn_enc_rval_t oer_encode_to_buffer(
+    const struct asn_TYPE_descriptor_s *type_descriptor,
+    const asn_oer_constraints_t *constraints,
+    const void *struct_ptr, /* Structure to be encoded */
+    void *buffer,           /* Pre-allocated buffer */
+    size_t buffer_size      /* Initial buffer size (maximum) */
+);
+
+/*
+ * Type of the generic OER encoder.
+ */
+typedef asn_enc_rval_t(oer_type_encoder_f)(
+    const struct asn_TYPE_descriptor_s *type_descriptor,
+    const asn_oer_constraints_t *constraints,
+    const void *struct_ptr,                    /* Structure to be encoded */
+    asn_app_consume_bytes_f *consume_bytes_cb, /* Callback */
+    void *app_key                              /* Arbitrary callback argument */
+);
+
+/*
+ * Write out the Open Type (X.696 (08/2015), #30).
+ * RETURN VALUES:
+ *  -1: Fatal error encoding the type.
+ *  >0: Number of bytes serialized.
+ */
+ssize_t oer_open_type_put(const struct asn_TYPE_descriptor_s *td,
+                          const asn_oer_constraints_t *constraints,
+                          const void *struct_ptr,
+                          asn_app_consume_bytes_f *consume_bytes_cb,
+                          void *app_key);
+
+
+/*
+ * Length-prefixed buffer encoding for primitive types.
+ */
+oer_type_encoder_f oer_encode_primitive;
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif	/* OER_ENCODER_H */