Log Message:
Update to Racket 5.2.1

Changes in Racket 5.2.1

* Performance improvements include the use of epoll()/kqueue()
  instead of select() for the Racket thread scheduler, cross-module
  inlining of small functions, and the use of SSE instead of x87 for
  JIT-compiled floating-point operations on platforms where SSE is
  always available (including x86_64 platforms).  A related change
  is the interning of literal numbers, strings, byte strings,
  characters, and regexps that appear in code and syntax objects.

* DrRacket uses a set of composable ray-traced icons available from
  the new `images' library collection.

* Typed Racket's `typecheck-fail' form allows macro creators to
  customize the error messages that Typed Racket produces.  This is
  especially useful when creating pattern matching macros.

* The performance of Redex's matcher has been substantially
  improved; depending on the model you should see improvements
  between 2x and 50x in the time it takes to reduce terms.

* Plots look nicer and are more correct at very small and very large
  scales.  New features include customizable dual axis ticks and
  transforms (e.g., log axes, date and currency ticks, axis interval
  collapse and stretch), stacked histograms, and 3D vector fields.
  The legacy `fit' function and libfit have been removed.

* The `2htdp/universe' library's `big-bang' form supports an
  experimental game pad key handler.

* The `db' library now supports nested transactions and PostgreSQL
  arrays.  Bugs involving MySQL authentication and memory corruption
  in the SQLite bindings have been fixed.

* The Macro Stepper tool in DrRacket no longer executes a program
  after expanding it.

* In the DMdA teaching languages, infinite recursive signatures
  ("streams", for example) with no intervening `mixed' are now
  supported, and the signatures of record definitions without fields
  now have generators for use with `property'.

* MysterX's ActiveX support is deprecated and will be removed in the
  next release.  MysterX's core COM functionality will become
  deprecated in the next release, but COM functionality will be
  supported for the foreseeable future as a compatibility layer over
  a forthcoming `ffi/com' library.