c++: pack in enumerator in lambda [PR100198]

c++: pack in enumerator in lambda [PR100198]

The GCC 8 lambda overhaul fixed most uses of lambdas in pack expansions, but
local enums and classes within such lambdas that depend on parameter packs
are still broken.  For now, give a sorry instead of an ICE or incorrect
error.

	PR c++/100198
	PR c++/100030
	PR c++/100282

gcc/cp/ChangeLog:

	* parser.cc (cp_parser_enumerator_definition): Sorry on parameter
	pack in lambda.
	(cp_parser_class_head): And in class attributes.
	* pt.cc (check_for_bare_parameter_packs): Sorry instead of error
	in lambda.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp0x/lambda/lambda-variadic13.C: Accept the sorry
	as well as the correct error.
	* g++.dg/cpp0x/lambda/lambda-variadic14.C: Likewise.
	* g++.dg/cpp0x/lambda/lambda-variadic14a.C: New test.
	* g++.dg/cpp0x/lambda/lambda-variadic15.C: New test.
	* g++.dg/cpp0x/lambda/lambda-variadic16.C: New test.