[pkg-php-pear] Symfony security updates (Was: unblock: symfony/2.3.21+dfsg-4)

["David Prévot"]

Hi Daniel,

> Please unblock package symfony
>
> It cherry-picks to security fixes from upstre[a]m:

IIRC, you were in touch with upstream to get in advance information about
security fixes (so we may prepare security backports in order get them in
stable in sync with upstream). What is the status?

I was lucky to notice this one quickly after the release, but would prefer
if we have more time to prepare it next time (since the 2.3 branch
receives a lot more than security fixes, simply cherry-picking a targeted
commit may not be enough in the not so distant future
).

Regards

David