[racket-dev] Release Announcement for v6.1

At Tue, 29 Jul 2014 06:31:21 -0700, Sam Tobin-Hochstadt wrote:
> Plumbers look like a fundamental new runtime system concept, and so I think
> we should mention them, even though most people won't use them.

At Tue, 29 Jul 2014 13:47:58 -0400, Matthias Felleisen wrote:
> +1 on plumbers, if only for the word :-) 

Ok, here's a draft bullet:

 * Plumbers generalize the flush-on-exit capability of primitive output
   ports to enable arbitrary flushing actions and to give programmers
   control over the timing of flushes (i.e., a composable `atexit`).
   New functions include `current-plumber`, `plumber-add-flush!`, and
   `plumber-flush-all`.