* setlsapwd.cc (setlsapwd): Use RtlSecureZeroMemory to delete password
	from memory.
	* setpwd.cc (client_request_setpwd::serve): Use RtlSecureZeroMemory to
	delete password from memory.
	* passwd.cc (pg_ent::enumerate_builtin): Convert pwd_builtins and
	grp_builtins to array of cygpsid pointers.  Replace SID strings with
	pointers to well known SIDs.
	* sec_helper.cc (well_known_local_service_sid): Define.
	(well_known_network_service_sid): Define.
	(trusted_installer_sid): Define.
	* security.h (well_known_local_service_sid): Declare.
	(well_known_network_service_sid): Declare.
	(trusted_installer_sid): Declare.
	* uinfo.cc (pwdgrp::fetch_account_from_windows): Throughout set acc_type
	to SidTypeUnknown if LookupAccountXXX function failed.  Create
	simplified passwd entry for non-user accounts, except for LocalSystem.
	Add comment.
	* libc/include/stdlib.h (strtold): Define if _HAVE_LONG_DOUBLE is
	defined.
	* libc/stdlib/strtold.c (strtold): Ditto.  Call strtod on systems
	with long double == double, _strtold otherwise.
	* pwdgrp.h (pwdgrp::is_passwd): New inline method.
	(pwdgrp::is_group): New inline method.
	(add_account_from_windows): Drop group argument from declaration.
	(fetch_account_from_windows): Ditto.
	(check_file): Ditto.
	(add_user_from_windows): Call add_account_from_windows accordingly.
	(add_group_from_windows): Ditto.
	* uinfo.cc (pwdgrp::add_account_from_windows): Drop group argument.
	Use is_group method instead.
	(pwdgrp::check_file): Ditto.
	(pwdgrp::fetch_account_from_windows): Ditto.
	* grp.cc: Accommodate aforementioned changes.
	* passwd.cc: Ditto.