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FLASHING.md says how to take a newer version of the colleague's tree (copy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

@@ -0,0 +1,74 @@
+/*
+ * 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 "asn_codecs_prim.h"
+#include "BOOLEAN.h"
+#include <errno.h>
+
+/*
+ * Decode the chunk of XML text encoding INTEGER.
+ */
+static enum xer_pbd_rval
+BOOLEAN__xer_body_decode(const asn_TYPE_descriptor_t *td, void *sptr,
+                         const void *chunk_buf, size_t chunk_size) {
+    BOOLEAN_t *st = (BOOLEAN_t *)sptr;
+    const char *p = (const char *)chunk_buf;
+
+    (void)td;
+
+    if(chunk_size && p[0] == 0x3c /* '<' */) {
+        switch(xer_check_tag(chunk_buf, chunk_size, "false")) {
+        case XCT_BOTH:
+            /* "<false/>" */
+            *st = 0;
+            break;
+        case XCT_UNKNOWN_BO:
+            if(xer_check_tag(chunk_buf, chunk_size, "true") != XCT_BOTH)
+                return XPBD_BROKEN_ENCODING;
+            /* "<true/>" */
+            *st = 1;  /* Or 0xff as in DER?.. */
+            break;
+        default:
+            return XPBD_BROKEN_ENCODING;
+        }
+        return XPBD_BODY_CONSUMED;
+    } else {
+        return XPBD_BROKEN_ENCODING;
+    }
+}
+
+
+asn_dec_rval_t
+BOOLEAN_decode_xer(const asn_codec_ctx_t *opt_codec_ctx,
+                   const asn_TYPE_descriptor_t *td, void **sptr,
+                   const char *opt_mname, const void *buf_ptr, size_t size) {
+    return xer_decode_primitive(opt_codec_ctx, td,
+                                sptr, sizeof(BOOLEAN_t), opt_mname, buf_ptr, size,
+                                BOOLEAN__xer_body_decode);
+}
+
+asn_enc_rval_t
+BOOLEAN_encode_xer(const asn_TYPE_descriptor_t *td, const void *sptr,
+                   int ilevel, enum xer_encoder_flags_e flags,
+                   asn_app_consume_bytes_f *cb, void *app_key) {
+    const BOOLEAN_t *st = (const BOOLEAN_t *)sptr;
+    asn_enc_rval_t er = {0, 0, 0};
+
+    (void)ilevel;
+    (void)flags;
+
+    if(!st) ASN__ENCODE_FAILED;
+
+    if(*st) {
+        ASN__CALLBACK("<true/>", 7);
+    } else {
+        ASN__CALLBACK("<false/>", 8);
+    }
+
+    ASN__ENCODED_OK(er);
+cb_failed:
+    ASN__ENCODE_FAILED;
+}