PR c++/90842
	* parser.c (cp_parser_decl_specifier_seq): For concept or typedef
	break early if CP_PARSER_FLAGS_ONLY_MUTABLE_OR_CONSTEXPR.
	For type specifiers, set CP_PARSER_FLAGS_NO_TYPE_DEFINITIONS
	if CP_PARSER_FLAGS_ONLY_MUTABLE_OR_CONSTEXPR is set.

	* g++.dg/cpp1y/lambda-generic-90842.C: New test.

Co-Authored-By: Jason Merrill <jason@redhat.com>

From-SVN: r278538