re PR c++/57 ([DR 325] GCC can't parse a non-parenthesized comma in a template-id within a default argument)

        PR c++/57
        * parser.c (cp_parser_parameter_declaration): Handle < ambiguity
        in default arguments.

Co-Authored-By: Liu Guanwei <liu_gw@163.com>

From-SVN: r134762