Log Message:
Update to Racket 5.3

Changes in Racket 5.3

* Submodules are nested module declarations that can be loaded and
  run independently from the enclosing module.  For an overview of
  submodules, see

    http://blog.racket-lang.org/2012/06/submodules.html

* The futures visualizer is a graphical profiling tool for parallel
  programs using futures.  The tool shows a detailed execution
  timeline depicting the migration of futures between threads, and
  gives detailed information about each runtime synchronization that
  occurred during program execution.  In addition, `would-be-future'
  is a special type of future that always executes sequentially and
  records all potential barricades a regular future would encounter.

* Optimization Coach (formerly Performance Report) reports
  information about Racket's inlining optimizations.  Optimization
  Coach can be launched in any language through the View menu.

* The new `images/flomap' library defines floating-point bitmaps and
  fast image processing operations on them.  It is written in Typed
  Racket, so Typed Racket code may use it without the cost of
  contract checks.

* The new `json' library supports parsing and generating JSON.
  (Originally based on Dave Herman's planet library.)

* `racket/string' is extended with a set of simplified string
  manipulation functions that are more convenient than using
  regexps.  `regexp-match*' and friends can now be used with new
  keyword arguments to return specific matched regexp group/s and
  gaps between matches.

* The new `racket/generic' library allows generic function
  definitions, which dispatch to methods added to a structure type
  via the new `#:methods' keyword.

* The `class' form supports declaring a method abstract.  An
  abstract method prevents a class from being instantiated unless it
  is overridden.

* The contract library comes with support for interfaces, generics,
  prompts, continuation-marks, and structs.

* Most error messages use a new multi-line format that is more
  consistent with contract errors and accommodates more information.

* Typed Racket supports function definitions with keyword arguments;
  the startup time of Typed Racket programs has been sharply
  reduced.

* The new `ffi/com' library replaces MysterX; a compatibility
  `mysterx' library remains, but without ActiveX support.  The new
  `ffi/unsafe/com' library offers a more primitive and direct way to
  use COM classes and methods.

* There is now a very complete completion code for zsh.  It is not
  included in the distribution though; get it at http://goo.gl/DU8JK
  (This script and the bash completions will be included in the
  standard installers in future versions.)

--- DEPRECATION ----------------------------------------------------

Effective this release:

  - The `tex2page' and `combinator-parser' libraries have been moved
    from the Racket distribution to PLaneT:

     (require (planet plt/tex2page))
     (require (planet plt/combinator-parser))

The following has been deprecated and will be removed in the
January 2013 release:

  - the `planet' command-line tool; use `raco planet' instead.

The following has been deprecated and will be removed in the
August 2013 release:

  - the `mzlib/class100' library; use `racket/class' instead.