patch applied (ghc-6.6/ghc): Fix bug exposed by conc052. A thread that was blocked on a blackhole

[Simon Marlow]

Wed Apr  4 02:40:21 PDT 2007  Simon Marlow <simonmar at microsoft.com>
  * Fix bug exposed by conc052.  A thread that was blocked on a blackhole
  but can now be woken up could possibly be treated as unreachable by
  the GC, and sent the NonTermination exception.
  
  This can give rise to spurious <<loop>>s in concurrent programs, so
  it's a good one to fix.

    M ./rts/GC.c -5 +14