GDB 17 release schedule proposal

[Joel Brobecker <brobecke@adacore.com>]

Hello everyone,

Now that the GDB 16.3 release is out, it's time to start thinking
about the GDB 17.x release cycle.

Here are the dates I propose we aim for:

  * Branching: Jun 21st
  * Release: Jul 26th

This is only 2 months away from the last release, so slightly
on the fast side, but it has the advantage of reducing our overlap
with the month of Aug, which is typically very slow. It also helps
keep the one major release every 6 months pace.

Let us know if you'd prefer some different dates.

And as always, please let us know if there are some pending issues
or changes that you think should make it to release 17 (with
a rationale for the suggestion please :-) ).

Thank you all!
-- 
Joel