removal of the old PHP-X.Y.Z release branches

Hi, we RMs started using the release branches (PHP-X.Y.Z) a while ago and we push those so that the we can work together easier when preparing/syncing the releases. As those branches are meaningless for the general public I would propose updating our current release process ( https://github.com/php/php-src/blob/master/README.RELEASE_PROCESS) so that when we create a new release branch (PHP-X.Y.Z) we also remove the old release branch (PHP-X.Y.Z-1). (we could even remove it after tagging the final, but in the past we had a couple of re-tags, so it is easier to just remove when creating the release branch for the next version). I would also propose removing all of the old release branches for now(only keeping the last one for each minor/major version). ps: I've also cc-ed the internals@ list so people won't freak out if/when we remove the old branches en masse. -- Ferenc Kovács @Tyr43l - http://tyrael.hu