Removed support for directly mocking a protected member function

Taking a function pointer on a base member protected function is actually invalid.
This could work with a pointer on the derived class member function, that is &derived::method instead of &base::method however there is no way to pass the derived class from MOCK_BASE_CLASS to the mock::detail::base helper if template classes are to be supported.

Anyway the now documented workaround is simple enough and the same as for private member functions.

As a side note the changes from ed36823235 might not be needed any more…

doc/example/limitations_private_method.cpp

@@ -1,29 +0,0 @@
-// http://turtle.sourceforge.net
-//
-// Copyright Mathieu Champlon 2014
-//
-// 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)
-
-#define BOOST_AUTO_TEST_MAIN
-#include <boost/test/auto_unit_test.hpp>
-#include <turtle/mock.hpp>
-
-namespace
-{
-//[ limitations_private_method_problem
-    class base
-    {
-    private:
-        virtual void method() = 0;
-    };
-//]
-
-//[ limitations_private_method_solution
-    MOCK_BASE_CLASS( mock_base, base )
-    {
-        MOCK_METHOD( method, 0, void() )
-    };
-//]
-}