Releasing 17.12.05, 18.12.01 and freezing R20

[Jacques Le Roux]

Hi All,

We have no longer any pending security issues, even post-auth ones (those with no CVE). As Marj J. Cox  - VP of ASF security - said once to me: <<"No 
CVE" is a great outcome>> ;)

I propose that

 * we release 17.12.05 as the last release of R17.
 * We release 18.12.01 as the first release of R18.
 * That we make R18 our current stable branch, and so R17 the old one.
 * And finally that we freeze a new R20 branch.

What do you people think?

If it's OK with everybody could you handle it, or part of it if we don't agree 
on all, Jacopo?

Thanks

Jaques