C++: fix-it hints suggesting accessors for private fields

gcc/cp/ChangeLog:
	* call.c (enforce_access): Add access_failure_info * param and use
	it to record access failures.
	* cp-tree.h (class access_failure_info): New class.
	(enforce_access): Add access_failure_info * param, defaulting to
	NULL.
	(lookup_member): Likewise.
	(locate_field_accessor): New function decl.
	(perform_or_defer_access_check): Add access_failure_info * param,
	defaulting to NULL.
	* search.c (lookup_member): Add access_failure_info * param and
	pass it on to call to perform_or_defer_access_check.
	(matches_code_and_type_p): New function.
	(field_access_p): New function.
	(direct_accessor_p): New function.
	(reference_accessor_p): New function.
	(field_accessor_p): New function.
	(struct locate_field_data): New struct.
	(dfs_locate_field_accessor_pre): New function.
	(locate_field_accessor): New function.
	* semantics.c (perform_or_defer_access_check): Add
	access_failure_info * param, and pass it on to call to
	enforce_access.
	* typeck.c (access_failure_info::record_access_failure): New method.
	(access_failure_info::maybe_suggest_accessor): New method.
	(finish_class_member_access_expr): Pass an access_failure_info
	instance to the lookup_member call, and call its
	maybe_suggest_accessor method afterwards.

gcc/testsuite/ChangeLog:
	* g++.dg/other/accessor-fixits-1.C: New test case.
	* g++.dg/other/accessor-fixits-2.C: New test case.
	* g++.dg/other/accessor-fixits-3.C: New test case.
	* g++.dg/other/accessor-fixits-4.C: New test case.

From-SVN: r248128