Only in 2.6.5-aa5: nonlinear-can-do-mlock

	Avoid truncate vs nonlinear BUG mentioned by Hugh Dickins on l-k.
	Give nonlinear only to privilegied users that knows how to avoid
	breaking the kernel. If local security doesn't matter disable-cap-mlock
	can be enabled and it'll give mlock and remap-file-pages too to every
	user. truncate must be fixed anyways to increase the strength of
	disable-cap-mlock but it gets low priority after moving the thing under
	sysctl, and I plan to keep the nonlinear hack forever under the sysctl
	for VM robusteness in providing _fair_ swapping to all processes.
	BTW, the mmap(MAP_POPULATE) API is horrible, there's no way to catch
	a failure with it, it doesn't return any retval, and I cannot fix it
	in my tree or I become ABI/API incompatible with linux 2.6, that's just
	a broken API that wants to be fixed properly in mainline despite the
	break of backwards compatibility.