grow-down auto extend segment) by allocating segment sized at
current stack size limit, and offsetting requested/returned address
as required
due to how normal virtual memory management work, allocating the
full sized stack memory segment up-front actually requires exactly same
amount of VA space and physical memory as the Linux 'grow' scheme and the
'grow' scheme is quite a lot more difficult to use in applications correctly,
so it's not very apparent why Linux introduced this feature at all
this fixes Thomas Klausner's Heroes3 crash, and might also
fix PR 26687 by Jan Schaumann
466a837559