Reinstate program incorrectly deleted in last commit.

test/cmd_line_check.cpp

@@ -0,0 +1,15 @@
+//  Copyright 2014 John Maddock.
+//
+//  Distributed under 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
+
+#ifndef __clang__
+#  error "This test is for Clang only"
+#endif
+
+int main()
+{
+	return 0;
+}