tunables overridability patch vs release

Re: https://patchwork.sourceware.org/project/glibc/patch/[email protected]/

So I originally left this bit out intentionally because (1) I thought
it would be hard, (2) it wasn't needed by most of the folks waiting
for the tunables work, and (3) I didn't expect the patch set to land
so close to a release.

However, tunables is in and it's already hit the press[*], including
the bit about overridability, because I implemented the parser side of
this already (needed by the AT_SECURE parts).  The patch turned out to
be fairly simple but still needs a reviewed-by.

Thus, I would like to consider this patch as "desirable" for this
release.  It was posted before the freeze, one could consider it a
bugfix and/or continuation of the main tunables patches, or we could
delay it and backport it later.

[*] https://www.phoronix.com/news/Glibc-System-Tunables