C++20 breaks broken print_log_value<wchar_t const*>::operator() even more

[CaseyCarter]

print_log_value<wchar_t const*>::operator():

test/include/boost/test/impl/test_tools.ipp

Lines 124 to 128 in 119a3a7

	void
	print_log_value<wchar_t const*>::operator()( std::ostream& ostr, wchar_t const* t )
	{
	ostr << ( t ? t : L"null string" );
	}

is completely bogus. Narrow streams (std::ostream& ostr) have no special support for pointer-to-wchar_t, so in C++17 and earlier the result is to call the void* stream insertion operator and output the pointer value rather than the characters it points to.

C++20 helpfully renders this function ill-formed by adding a deleted stream insertion operator for std::ostream and wchar_t const*; see http://eel.is/c++draft/diff.cpp17.input.output#3.

I'm not sure why this function exists, but I suspect it is not fit for purpose.

[raffienficiaud]

Fixed via #252