Partially revert change from 2006-10-22. GetSecurityInfo messes up

	Partially revert change from 2006-10-22.  GetSecurityInfo messes up
	user information on NT4.
	* sec_helper.cc (security_descriptor::malloc): Drop LocalAlloc
	considerations.
	(security_descriptor::realloc): Ditto.
	(security_descriptor::free): Ditto.
	* security.cc (get_reg_security): Reinstantiate.
	(get_nt_object_security): Revert to using NtQuerySecurityObject.
	* security.h (class security_descriptor): Drop type member.
	Accommodate throughout.
	(security_descriptor::size): Constify.
	(security_descriptor::copy): Ditto.