ADD: new track message, Entity class and Position class

libs/geographiclib/examples/example-GARS.cpp

@@ -0,0 +1,39 @@
+// Example of using the GeographicLib::GARS class
+
+#include <iostream>
+#include <iomanip>
+#include <exception>
+#include <string>
+#include <GeographicLib/GARS.hpp>
+
+using namespace std;
+using namespace GeographicLib;
+
+int main() {
+  try {
+    {
+      // Sample forward calculation
+      double lat = 57.64911, lon = 10.40744; // Jutland
+      string gars;
+      for (int prec = 0; prec <= 2; ++prec) {
+        GARS::Forward(lat, lon, prec, gars);
+        cout << prec << " " << gars << "\n";
+      }
+    }
+    {
+      // Sample reverse calculation
+      string gars = "381NH45";
+      double lat, lon;
+      cout << fixed;
+      for (int len = 5; len <= int(gars.size()); ++len) {
+        int prec;
+        GARS::Reverse(gars.substr(0, len), lat, lon, prec);
+        cout << prec << " " << lat << " " << lon << "\n";
+      }
+    }
+  }
+  catch (const exception& e) {
+    cerr << "Caught exception: " << e.what() << "\n";
+    return 1;
+  }
+}