c++: lambda in default type template-argument [PR100091]

c++: lambda in default type template-argument [PR100091]

My patch for 99478 relied on local_variables_forbidden_p for distinguishing
between a template parameter and its default argument, but that flag wasn't
set for a default type template-argument.

gcc/cp/ChangeLog:

	PR c++/100091
	PR c++/99478
	* parser.c (cp_parser_default_type_template_argument): Set
	parser->local_variables_forbidden_p.

gcc/testsuite/ChangeLog:

	PR c++/100091
	* g++.dg/cpp2a/lambda-uneval15.C: New test.