Add Authz class to compute exact POSIX user perms in a security descriptor

Add Authz class to compute exact POSIX user perms in a security descriptor

	* autoload.cc (AuthzAccessCheck): Import.
	(AuthzFreeContext): Import.
	(AuthzInitializeContextFromSid): Import.
	(AuthzInitializeContextFromToken): Import.
	(AuthzInitializeResourceManager): Import.
	* sec_helper.cc (get_sids_info): Remove.
	(class authz_ctx_cache_entry): New class.
	(class authz_ctx_cache): New class.
	(class authz_ctx): New class.
	(authz_get_user_attribute): New function.
	* security.h (get_sids_info): Drop prototype.
	(authz_get_user_attribute): Add prototype.
	* winlean.h (_AUTHZ_): Define.