[racket-dev] release blurb for 5.1.1

More things:

Casey:
  - Redex version of Jay's continuation mark transformation (3250ff84)
  - Other redex news?

Vincent:
  - TR's numeric tower is now built from unions of non-overlapping base
    types.  (d4c93cc1)

Vincent/Sam: other TR news?

Vincent/Matthew: single precision flonums?

Matthew:
  - `file/resource'?
  - Recent speed thing.

Robby:
- make hard links be version specific (4f165d3b)?
- 2htdp/image news?
- builds on osx 64 bits

James/Matthew: futures news?  (future semaphores, `future' in future,
  more ...)

Generators have formals (generator formals body ...+)

Ryan: `racket/syntax' etc

-- 
          ((lambda (x) (x x)) (lambda (x) (x x)))          Eli Barzilay:
                    http://barzilay.org/                   Maze is Life!