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FLASHING.md says how to take a newer version of the colleague's tree (copy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/facilities/path_point.cpp

@@ -0,0 +1,29 @@
+#include <vanetza/facilities/path_point.hpp>
+#include <boost/units/cmath.hpp>
+#include <boost/units/systems/si/prefixes.hpp>
+
+namespace vanetza
+{
+namespace facilities
+{
+
+const units::Length cREarthMeridian = units::Length(6378.137 * units::si::kilo * units::si::meters);
+
+PathPoint::PathPoint()
+{
+}
+
+units::Length chord_length(const PathPoint& a, const PathPoint& b)
+{
+    const units::Angle lat1(a.latitude);
+    const units::Angle lon1(a.longitude);
+    const units::Angle lat2(b.latitude);
+    const units::Angle lon2(b.longitude);
+
+    return cREarthMeridian *
+        acos(cos(lat1) * cos(lat2) * cos(lon1 - lon2) + sin(lat1) * sin(lat2))
+        / units::si::radian ;
+}
+
+} // namespace facilities
+} // namespace vanetza