ANNOUNCE: MonadCatchIO-foreign

[Evan Laforge]

> Here's the ticket:
>
> http://hackage.haskell.org/trac/ghc/ticket/2917
>
> Lennart's patch added allocaBytesAligned to Foreign.Marshal.Alloc, but we'll
> have to do a library proposal to add that.
>
> If you can reproduce the assertion failure, please submit a bug report.

Unfortunately this assertion failure, though it will always happen
eventually, has proven to be a real pain to track down.  I filed a bug
report a long time ago, closed it when I mistakenly thought I had
fixed the problem, and now I'm waiting until I've narrowed things down
some more.

I'm no longer so suspicious of allocaBytes since it still happened
after I replaced it with alloca, which, contrary to the trac ticket,
does appear to use allocaBytesAligned.  And I don't really see how it
could cause memory corruption anyway...