*ping* generic atomicity.h

[Benjamin Kosnik]

>Without either your patch or always using the i486 version of atomicity.h (as
>per the submission at http://gcc.gnu.org/ml/libstdc++/2002-12/msg00232.html)
>I cannot build libstdc++ for i386-pc-mingw with trunk or 3.3
>
>With the patch I can build i386-pc-cygwin (which has _GTHREAD_MUTEX_INIT) and
>i386-pc-mingw (which doesn't).

Phil's call, either look ok from where I sit.

-benjamin