Add module support and tests.

test/module/config/has_module_support.cpp

@@ -0,0 +1,26 @@
+/*
+ *
+ * Copyright (c) 2022
+ * John Maddock
+ *
+ * Use, modification and distribution are subject to the 
+ * Boost Software License, Version 1.0. (See accompanying file 
+ * LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+ *
+ */
+
+module;
+
+#include <memory>
+
+export module test_support;
+
+export template <class T> struct pimpl
+{
+private:
+   std::shared_ptr<T> data;
+public:
+   pimpl(const T& x) : data(new T(x)) {}
+   pimpl() = default;
+};
+