[PATCH] Created tunable to force small pages on stack allocation.

[Cupertino Miranda]

Hi everyone,

This patch is the result of the following RFC:
https://sourceware.org/pipermail/libc-alpha/2023-March/146203.html

It introduces the tunable glibc.pthread.stack_hugetlb to control when
stack allocation should be allowed to be mapped in hugetls.
The purpose of this tunable is to allow better control on RSS for
applications/systems that rely on having hugepages enabled, for
performance reasons, but still wish to want to keep RSS to a minimal
when allocating lots of threads.

Looking forward to your comments and suggestions.

Best regards,
Cupertino