[plt-dev] Release Announcement for v4.2.3, second call

The release announcement sketch items that I have so far is below, and
some more items that I don't know if they should be mentioned, or how
to describe them.

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* The unit test framework for the teaching languages provides
  `check-member-of' and `check-range' for checking "random
  functions", i.e., "functions" that may produce several different
  results for one and the same argument.

* Added a new image library, `2htdp/image'.  Significant changes
  from `htdp/image':
  - copying and pasting does not introduce jaggies
  - `equal?' comparisons are more efficient
  - added rotation & scaling
  - got rid of pinholes (new overlay, beside, above functions based
    on bounding boxes)

* The `scheme/vector' library provides common vector operations
  (also reprovided by `scheme').

* The `scheme/promise' library provides several new kinds of
  promises with alternatives execution strategies.

* New port-reading utilities: `in-port', `port->list', `file->list'.

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* added support for changing toolbar buttons based on the #lang
  line, use that for #lang scribble/base

* added `path-up' to scheme/require

* syntax/parse extensions (~var, ~literal, ~and, ~not, etc)

* change _pointer to mean a reference to non-GCed memory; add
  _gcpointer

* scheme/unsafe/ops? (wasn't mentioned last time)

* upgrade Boehm GC to v7.1
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-- 
          ((lambda (x) (x x)) (lambda (x) (x x)))          Eli Barzilay:
                    http://barzilay.org/                   Maze is Life!