[racket-dev] Release Announcement for v5.3.1

The release announcement sketch that I have so far is below.  Please
mail me new items and/or edits.
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mflatt:
  - new case implementation (by Jon Zeppieri) (7ccf0efce9)
  - ffi/unsafe: show errors from finalizers (1d8791c7c4)
  - new ffi/unsafe/custodian (42ef79c2ad)
  - ffi/com improvements (4e5b46405d, etc)
  - for/vector improvements (8a26d83651)
  - add dynamic-get-field, etc (ba56fd72da)
  - thread initial prompt change (2f7d4b5eaf)
  - add racket/format (b53e458e3f)
  - log-error etc do format (fc0d605d18)
  - add define-logger etc (d92b9cb404)
  - add current-compiled-file-roots, etc (4f351dd6b1)
  - JIT stack traces on win64 (98cf0429f8)
  - add #:break, #:final to for forms (fc52248446)
  - rackunit now part of mz distro (e9f522ba94)

robby:
  - define-judgment-form improvements (0369342bfe)
  - "blue boxes" (0c6734f782)

frtime:
  - Patrick Mahoney ported frtime to racket lang (64e9bdd92d, 
01ec2d3fde, etc)

stamourv:
  - scheme language deprecation notice (68260a6c86)
  - compat: packages, mutable lists (800a328fe6)
  - NaN included in all float types (a6d5a98b61)
  - optimization coach changes?

samth:
  - type->contract fixes/changes (9e1cf579a4, 962f2472e1)
  - add #:opaque and #:struct to require/typed (9054d0db7d)

ryanc:
  - readline speedup (5 vs 6) (ae843f9a62)
  - db postrgresql 9.2 support, etc (9d34f0f147)

sperber:
  - provide 'provide' in DMdA langs (41d6d8f579)

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