FYI: AccessController speedup

[Tom Tromey]

>>>>> "Gary" == Gary Benson <gbenson@redhat.com> writes:

Gary> This commit changes VMAccessController to use an instance
Gary> variable in Thread to store its state.  On my Tomcat benchmark
Gary> this improves performace from 2400 to 2700 requests per second.

Wow.  If shaving cycles here helps... maybe on supported platforms we
should be using real TLS?  Search for HAVE_TLS in natClass.cc to see
how we're already using it.

But maybe it is just avoiding the gratuitous overhead of ThreadLocal
that is a win.

Tom