[Bug c++/58898] Adding default template argument to class template with "most vexing parse" causes compile error

[paolo.carlini at oracle dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58898

--- Comment #1 from Paolo Carlini <paolo.carlini at oracle dot com> ---
This is already fixed mainline and 4.9.1. I'm adding the testcase and closing
the bug.