re PR c++/27884 (bogus error: invalid use of 'register' in linkage specification)

re PR c++/27884 (bogus error: invalid use of 'register' in linkage specification)

	PR c++/27884
	* decl.c (have_extern_spec): Remove.
	(start_decl): Do not check have_extern_spec.
	(start_function): Likewise.
	* cp-tree.h (have_extern_spec): Remove.
	* parser.c (cp_parser_linkage_specification): Don't set
	have_extern_spec.
	(cp_parser_init_declarator): Likewise.
	(cp_parser_parameter_declaration): Do not treat parameters as
	within the scope of an unbraced linkage specification.
	PR c++/27884
	* g++.dg/parse/linkage2.C: New test

From-SVN: r114727