Reimplement handling of lambdas in templates.

	* cp-tree.h (LAMBDA_FUNCTION_P): Check DECL_DECLARES_FUNCTION_P.
	* decl.c (start_preparsed_function): Call start_lambda_scope.
	(finish_function): Call finish_lambda_scope.
	* init.c (get_nsdmi): Call start/finish_lambda_scope.
	* lambda.c (start_lambda_scope): Only ignore VAR_DECL in a function.
	* parser.c (cp_parser_function_definition_after_declarator): Don't
	call start/finish_lambda_scope.
	* pt.c (retrieve_specialization): Ignore lambda functions in
	templates.
	(find_parameter_packs_r): Ignore capture proxies.  Look into
	lambdas.
	(check_for_bare_parameter_packs): Allow bare packs in lambdas.
	(tsubst_default_argument): Call start/finish_lambda_scope.
	(tsubst_function_decl): Handle lambda functions differently.
	(tsubst_template_decl): Likewise.
	(tsubst_expr) [DECL_EXPR]: Skip closure declarations and capture
	proxies.
	(tsubst_lambda_expr): Create a new closure rather than instantiate
	the one from the template.
	(tsubst_copy_and_build): Don't register a specialization of a pack.
	(regenerate_decl_from_template): Call start/finish_lambda_scope.
	(instantiate_decl): Remove special lambda function handling.
	* semantics.c (process_outer_var_ref): Remove special generic lambda
	handling.  Don't implicitly capture in a lambda in a template.  Look
	for an existing proxy.
	* class.c (current_nonlambda_class_type): Use decl_type_context.

From-SVN: r251433