[racket-dev] Release Announcement for v6.0.1

The release announcement sketch that I have so far is below.  Please
mail me new items and/or edits.
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mflatt:
- 2x bitmaps (037a211f, e47a90cc, etc); file/convertible (eda4f357)
- retina displays (7dc63162)
- dc alignment scale (582e9925)
- bignum performance (780d6ae5)
- added syntax/wrap-modbeg (bfda0665)
- treat FFI primitives like other primitives (eff53cde)
- add PLTUSERHOME (e4ce0d03)
- fix bignum allocation (efa19918)
- add racket/undefined (8abf7825, 74f82bbd)

robby:
- check syntax info even with syntax errors (09920bd8)
- contract system change, more first-order-friendly (c321f6dd)
- class/c changes (2989918a, 7bec967c, 4f65d57f, 59f57b1b)

vincent:
- contract profiler (cc0e6763, 7495243d, etc)
- make f[lx]vectors sequences (8e32e6e4)

asumu:
- TR :-less syntax (e6e3ab4e, 45d36579, 37b09521, etc)
- explain/warn about Class types?
- TR recursive type aliases (a8cc430d)

samth:
- web pages? (154b5453, etc)

neil:
- plot 3D BSP tree (a515e7ce)
- PDF/PS scaling changed to 1.0x1.0 (efc46ded)

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