My next step in handling stale PRs

[Mark J Cox]

We have over 50 PRs that are in the state where they are held
requiring a CLA, and stale (over 30 days since any comments).  My
intention is to have my script ping all these PRs with a comment like
this:

openssl-machine: This PR has the label "hold: cla required" and is
stale: it has not been updated in X days.   Note that this PR may be
automatically closed in the future if no CLA is provided.  For CLA
help see https://www.openssl.org/policies/cla.html

In another month we can decide it we want to autoclose them (note that
any comment, label change, etc, made to the PR after the above will
reset the timer and take it out of the list of possible ones to close)

I'll run it later in the week to give people a chance to voice any
comments or concerns.

Mark