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FLASHING.md says how to take a newer version of the colleague's tree (copy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

@@ -0,0 +1,103 @@
+/*
+ * 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 "REAL.h"
+
+asn_enc_rval_t
+REAL_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 REAL_t *st = (const REAL_t *)sptr;
+    asn_enc_rval_t er = {0,0,0};
+    double d;
+
+    (void)ilevel;
+
+    if(!st || !st->buf || asn_REAL2double(st, &d))
+        ASN__ENCODE_FAILED;
+
+    er.encoded = REAL__dump(d, flags & XER_F_CANONICAL, cb, app_key);
+    if(er.encoded < 0) ASN__ENCODE_FAILED;
+
+    ASN__ENCODED_OK(er);
+}
+
+/*
+ * Decode the chunk of XML text encoding REAL.
+ */
+static enum xer_pbd_rval
+REAL__xer_body_decode(const asn_TYPE_descriptor_t *td, void *sptr,
+                      const void *chunk_buf, size_t chunk_size) {
+    REAL_t *st = (REAL_t *)sptr;
+    double value;
+    const char *xerdata = (const char *)chunk_buf;
+    char *endptr = 0;
+    char *b;
+
+    (void)td;
+
+    if(!chunk_size) return XPBD_BROKEN_ENCODING;
+
+    /*
+     * Decode an XMLSpecialRealValue: <MINUS-INFINITY>, etc.
+     */
+    if(xerdata[0] == 0x3c /* '<' */) {
+        size_t i;
+        for(i = 0; i < sizeof(specialRealValue) / sizeof(specialRealValue[0]); i++) {
+            struct specialRealValue_s *srv = &specialRealValue[i];
+            double dv;
+
+            if(srv->length != chunk_size
+            || memcmp(srv->string, chunk_buf, chunk_size))
+                continue;
+
+            /*
+             * It could've been done using
+             * (double)srv->dv / real_zero,
+             * but it summons fp exception on some platforms.
+             */
+            switch(srv->dv) {
+            case -1: dv = - INFINITY; break;
+            case 0: dv = NAN;	break;
+            case 1: dv = INFINITY;	break;
+            default: return XPBD_SYSTEM_FAILURE;
+            }
+
+            if(asn_double2REAL(st, dv))
+                return XPBD_SYSTEM_FAILURE;
+
+            return XPBD_BODY_CONSUMED;
+        }
+        ASN_DEBUG("Unknown XMLSpecialRealValue");
+        return XPBD_BROKEN_ENCODING;
+    }
+
+    /*
+     * Copy chunk into the nul-terminated string, and run strtod.
+     */
+    b = (char *)MALLOC(chunk_size + 1);
+    if(!b) return XPBD_SYSTEM_FAILURE;
+    memcpy(b, chunk_buf, chunk_size);
+    b[chunk_size] = 0;	/* nul-terminate */
+
+    value = strtod(b, &endptr);
+    FREEMEM(b);
+    if(endptr == b) return XPBD_BROKEN_ENCODING;
+
+    if(asn_double2REAL(st, value))
+        return XPBD_SYSTEM_FAILURE;
+
+    return XPBD_BODY_CONSUMED;
+}
+
+asn_dec_rval_t
+REAL_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(REAL_t), opt_mname,
+                                buf_ptr, size, REAL__xer_body_decode);
+}