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FLASHING.md says how to take a newer version of the colleague's tree (copy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/geodesy/m49_code.hpp

@@ -0,0 +1,49 @@
+#pragma once
+#include <cstdint>
+#include <functional>
+
+namespace vanetza
+{
+namespace geodesy
+{
+
+/**
+ * Standard country or area codes for statistical use by M49 standard.
+ * \see https://unstats.un.org/unsd/methodology/m49/
+ */
+class M49Code
+{
+public:
+    explicit constexpr M49Code(uint16_t value) : m_value(value) {}
+    constexpr uint16_t value() const { return m_value; }
+
+    bool operator==(M49Code other) const { return m_value == other.m_value; }
+    bool operator!=(M49Code other) const { return m_value != other.m_value; }
+
+private:
+    uint16_t m_value;
+};
+
+} // namespace geodesy
+} // namespace vanetza
+
+namespace std
+{
+template<>
+struct hash<vanetza::geodesy::M49Code>
+{
+    std::size_t operator()(vanetza::geodesy::M49Code code) const
+    {
+        return std::hash<uint16_t>{}(code.value());
+    }
+};
+
+template<>
+struct less<vanetza::geodesy::M49Code>
+{
+    bool operator()(vanetza::geodesy::M49Code a, vanetza::geodesy::M49Code b) const
+    {
+        return a.value() < b.value();
+    }
+};
+} // namespace std