externals: Update boost to 1.72 and add Boost Context

boost/winapi/detail/cast_ptr.hpp

@@ -0,0 +1,37 @@
+/*
+ * Copyright 2015 Andrey Semashev
+ *
+ * Distributed under the Boost Software License, Version 1.0.
+ * See http://www.boost.org/LICENSE_1_0.txt
+ */
+
+#ifndef BOOST_WINAPI_DETAIL_CAST_PTR_HPP_INCLUDED_
+#define BOOST_WINAPI_DETAIL_CAST_PTR_HPP_INCLUDED_
+
+#include <boost/winapi/config.hpp>
+
+#ifdef BOOST_HAS_PRAGMA_ONCE
+#pragma once
+#endif
+
+namespace boost {
+namespace winapi {
+namespace detail {
+
+//! This class is used to automatically cast pointers to the type used in the current Windows SDK function declarations
+class cast_ptr
+{
+private:
+    const void* m_p;
+
+public:
+    explicit BOOST_FORCEINLINE cast_ptr(const void* p) BOOST_NOEXCEPT : m_p(p) {}
+    template< typename T >
+    BOOST_FORCEINLINE operator T* () const BOOST_NOEXCEPT { return (T*)m_p; }
+};
+
+}
+}
+}
+
+#endif // BOOST_WINAPI_DETAIL_CAST_PTR_HPP_INCLUDED_