[racket-dev] release blurb for 5.1.1

Here are some suggested items for the 5.1.1 release announcement. Please
respond with any additions/deletions. The stuff in parentheses are short
git sha1's. Use 'git show 12ab345' to see the commit.

ryan:
  * new ffi/file module (..needs description..) (9bc3457bb)

matthew
  * Removed drscheme, mred, and mred.app although mred for unix still
exists (8d9e10f34e)
  * The installed version of libffi can be used instead of the
distributed version (f3c3bb4441c)
  * `touch' and `future' are safe functions to execute inside futures
(857003378 3bf0f800a76)
  * A new streams library compatible with `for' has been added to the
racket collection as `racket/stream' (e652546bf52)
  * list-box% now supports multi-column (137d96c08917)

eli
  * chrome is a supported browser in drracket (52ca08a8a9a)
  * All 3rd party copyrighted code has had their licenses clarified or
changed to be compatible with the LGPL (f6f7e4eb3502 a3d00a910afb)

robby
  * Added a widget to the status line of DrRacket that can toggle line
numbers (c4e0559db4ca37)
  * The module browser graph is rendered much faster. (e928bd840c02)
  * Added `overlay/align', `underlay/align', `overlay/align/offset' and
'underlay/align/offset' (c1668d894e210)

stephen
  * The stepper now supports lazy racket (da456f2e37e54)

kathy
  * Addition of `define-wish' to the teaching languages and
corresponding addition of support for wishes in test reports and
check-expects (7758f508c56)