Heads up: malloc change

[Andrew Doran <ad%netbsd.org@localhost>]

Hi,

I just enabled CPU-based arena selection in malloc(), which helps some
multithreaded programs under high load. An unknown bug was causing this
to fail before, but I no longer see this happening. It's possible that
it's fixed or masked somehow. If you see an odd crash from a multithreaded
application that wasn't occuring before this change, please let me know.

Thanks,
Andrew