Keep vanetza-idf in obu-firmware, so a plain clone builds the firmware

obu-firmware builds against the vanetza-idf C-ITS library, which until now
came from the colleague's microbu-esp32c5 tree beside the repository and was
not tracked here, so a clone of this repository could not build the firmware
it ships. The library alone is now part of obu-firmware, as
obu-firmware/external/vanetza-idf: their external/vanetza-idf at commit
cf4b99f, unchanged (9775 files; see its PROVENANCE.md). CMake takes it from
there by default; -DVANETZA_IDF_DIR still points the build elsewhere.

The rest of the colleague's tree (their own VAM firmware, PKI tooling,
station-link Python tools, the V2X2MAP bridge) stays out of this repository
and gitignored; nothing is pushed to their repository. NOTES.md, docs/06,
TODO.md and the pcap verifier's usage line point at the new location.

obu-firmware/external/vanetza-idf/vanetza/asn1/support/xer_encoder.h

@@ -0,0 +1,83 @@
+/*-
+ * Copyright (c) 2004-2017 Lev Walkin <vlm@lionet.info>. All rights reserved.
+ * Redistribution and modifications are permitted subject to BSD license.
+ */
+#ifndef	_XER_ENCODER_H_
+#define	_XER_ENCODER_H_
+
+#include "asn_application.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+struct asn_TYPE_descriptor_s;	/* Forward declaration */
+
+/* Flags used by the xer_encode() and (*xer_type_encoder_f), defined below */
+enum xer_encoder_flags_e {
+	/* Mode of encoding */
+	XER_F_BASIC	= 0x01,	/* BASIC-XER (pretty-printing) */
+	XER_F_CANONICAL	= 0x02	/* Canonical XER (strict rules) */
+};
+
+/*
+ * The XER encoder of any type. May be invoked by the application.
+ * Produces CANONICAL-XER and BASIC-XER depending on the (xer_flags).
+ */
+asn_enc_rval_t xer_encode(const struct asn_TYPE_descriptor_s *type_descriptor,
+                          const void *struct_ptr, /* Structure to be encoded */
+                          enum xer_encoder_flags_e xer_flags,
+                          asn_app_consume_bytes_f *consume_bytes_cb,
+                          void *app_key /* Arbitrary callback argument */
+);
+
+/*
+ * The variant of the above function which dumps the BASIC-XER (XER_F_BASIC)
+ * output into the chosen file pointer.
+ * RETURN VALUES:
+ * 	 0: The structure is printed.
+ * 	-1: Problem printing the structure.
+ * WARNING: No sensible errno value is returned.
+ */
+int xer_fprint(FILE *stream, const struct asn_TYPE_descriptor_s *td,
+               const void *struct_ptr);
+
+/*
+ * A helper function that uses XER encoding/decoding to verify that:
+ * - Both structures encode into the same BASIC XER.
+ * - Both resulting XER byte streams can be decoded back.
+ * - Both decoded structures encode into the same BASIC XER (round-trip).
+ * All of this verifies equivalence between structures and a round-trip.
+ * ARGUMENTS:
+ *  (opt_debug_stream)  - If specified, prints ongoing details.
+ */
+enum xer_equivalence_e {
+    XEQ_SUCCESS,          /* The only completely positive return value */
+    XEQ_FAILURE,          /* General failure */
+    XEQ_ENCODE1_FAILED,   /* First structure XER encoding failed */
+    XEQ_ENCODE2_FAILED,   /* Second structure XER encoding failed */
+    XEQ_DIFFERENT,        /* Structures encoded into different XER */
+    XEQ_DECODE_FAILED,    /* Decode of the XER data failed */
+    XEQ_ROUND_TRIP_FAILED /* Bad round-trip */
+};
+enum xer_equivalence_e xer_equivalent(
+    const struct asn_TYPE_descriptor_s *type_descriptor, const void *struct1,
+    const void *struct2, FILE *opt_debug_stream);
+
+/*
+ * Type of the generic XER encoder.
+ */
+typedef asn_enc_rval_t(xer_type_encoder_f)(
+    const struct asn_TYPE_descriptor_s *type_descriptor,
+    const void *struct_ptr, /* Structure to be encoded */
+    int ilevel,             /* Level of indentation */
+    enum xer_encoder_flags_e xer_flags,
+    asn_app_consume_bytes_f *consume_bytes_cb, /* Callback */
+    void *app_key                              /* Arbitrary callback argument */
+);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif	/* _XER_ENCODER_H_ */