Comment 4 for bug 1757517

This is a continuation of issue 10643.

Using test case from issue 10643 (will reattach shortly),
built with -DCRASH results in:

do_aio_write: Invalid argument
do_aio_write: Invalid argument
failure: Invalid argument
failure: Invalid argument

AFAICT, this is happening because size of TLS and TCB is subtracted from
the stack size that the application requested (in the test case, aio_write
is trying to create a thread with 16K stack, but if user requested a thread
with small stack size, pthread_create would have failed just as well).

Since glibc is the only library that knows TLS and TCB sizes, shouldn't
it *add* these sizes to the user requested size, so the user gets exactly
16K of stack he asked for, and not 16K minus "some value we wouldn't
tell you"?