patch applied (ghc): recordMutable: test for gen>0 before calling recordMutableCap

[Simon Marlow]

Wed Oct 17 05:56:57 PDT 2007  Simon Marlow <simonmar at microsoft.com>
  * recordMutable: test for gen>0 before calling recordMutableCap
  For some reason the C-- version of recordMutable wasn't verifying that
  the object was in an old generation before attempting to add it to the
  mutable list, and this broke maessen_hashtab.  This version of
  recordMutable is only used in unsafeThaw#.

    M ./includes/Cmm.h -4 +8