[racket-dev] drafting the v5.1 release announcement

Let's get the ball rolling on the release announcement. Here are draft
bullets for the drawing and GUI libraries:

 * The `racket/draw' library --- which implements the drawing half the
   GUI toolkit --- is a new implementation built on top of the Cairo
   drawing library and the Pango text-rendering library.

   The `racket/draw' library can be used independent of the
   `racket/gui/base' library and without a graphics display (e.g.,
   without an X11 connection).

   The new library has one small incompatibility with the old GUI
   toolbox: 'xor drawing is no longer supported. The new library has
   many additional features: rotation and general affine
   transformations, PDF and SVG drawing contexts, gradients, and
   alpha-channel bitmaps.

 * The `racket/gui/base' library is a new implementation built on top
   of Win32 under Windows, Cocoa (instead of Carbon) under Mac OS X,
   and Gtk (instead of Xt) under Unix/X.

   Unix/X users will see the biggest difference with this change.
   DrRacket and all Racket GUI programs take on the desktop theme for
   menus, buttons, and other GUI widgets.

   The GRacket executable is no longer strictly necessary for running
   GUI programs, because the `racket/gui/base' library can be used from
   Racket. To the degree that a platform distinguishes GUI and console
   applications, however, the GRacket executable still offers some
   additional GUI-specific functionality (e.g., single-instance
   support).

   The new library includes small incompatibilities with the old GUI
   toolbox: the `send-event', `current-ps-afm-file-paths', and
   `current-ps-cmap-file-paths' functions have been removed. The
   `racket/gui/base' library re-exports `racket/draw', so it includes
   the same drawing functionality as before (except for 'xor drawing).