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FLASHING.md says how to take a newer version of the colleague's tree (copy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

@@ -0,0 +1,45 @@
+/*
+ * 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 "GeneralizedTime.h"
+#include <errno.h>
+
+#ifdef __CYGWIN__
+#include "/usr/include/time.h"
+#else
+#include <time.h>
+#endif  /* __CYGWIN__ */
+
+asn_enc_rval_t
+GeneralizedTime_encode_der(const asn_TYPE_descriptor_t *td, const void *sptr,
+                           int tag_mode, ber_tlv_tag_t tag,
+                           asn_app_consume_bytes_f *cb, void *app_key) {
+    GeneralizedTime_t *st;
+    asn_enc_rval_t erval = {0,0,0};
+    int fv, fd;  /* seconds fraction value and number of digits */
+    struct tm tm;
+    time_t tloc;
+
+    /*
+     * Encode as a canonical DER.
+     */
+    errno = EPERM;
+    tloc = asn_GT2time_frac((const GeneralizedTime_t *)sptr, &fv, &fd, &tm,
+                            1);  /* Recognize time */
+    if(tloc == -1 && errno != EPERM) {
+        /* Failed to recognize time. Fail completely. */
+        ASN__ENCODE_FAILED;
+    }
+
+    st = asn_time2GT_frac(0, &tm, fv, fd, 1);  /* Save time canonically */
+    if(!st) ASN__ENCODE_FAILED;                /* Memory allocation failure. */
+
+    erval = OCTET_STRING_encode_der(td, st, tag_mode, tag, cb, app_key);
+
+    ASN_STRUCT_FREE(*td, st);
+
+    return erval;
+}