Currently, there is no check that %printer ... <foo> (nor
%destructor) is about an existing <foo> type. This C++ test had
it wrong (<::std::string> vs. <std::string>).
* tests/c++.at (AT_CHECK_VARIANTS): In list.yy, redefine the
pretty-printing of lists into something better for parser traces.
Update the expected output.
Fix correspondance between %type/%token and %printer.
f5da8149a2