Optional: Move optional-lite to the include/third-party directory

This fixes the use case of adding the include folder
manually to an outside project.

include/icsneo/third-party/optional-lite/example/02-nodefltctor.cpp

@@ -0,0 +1,36 @@
+#include "nonstd/optional.hpp"
+
+#include <iostream>
+#include <vector>
+
+using nonstd::optional;
+
+struct V
+{
+    int v;
+
+    V( int v )
+    : v( v ) {}
+};
+
+int main()
+{
+    try
+    {
+        int x = 42;
+//      V s;        // V has no default constructor
+        V t(x);     // Ok
+
+        std::vector< optional<V> > v(3);
+        v[0] = t;
+
+        std::cout << "v[0].value().v: " << v[0].value().v << "\n";
+        std::cout << "v[1].value().v: " << v[1].value().v << "\n";
+    }
+    catch( std::exception const & e )
+    {
+        std::cout << "Error: " << e.what() << "\n";
+    }
+}
+
+// cl -nologo -W3 -EHsc -I../include 00-nodefltctor.cpp && 00-nodefltctor