Fix 64 bit Windows warning.
Fix 64 bit Windows warning.

robojukie/simbody,elkingtonmcb/simbody,chrisdembia/simbody,elkingtonmcb/simbody,scamille/simbody,robojukie/simbody,elen4/simbody,Gjacquenot/simbody,chrisdembia/simbody,scamille/simbody,elen4/simbody,robojukie/simbody,elkingtonmcb/simbody,simbody/simbody,Gjacquenot/simbody,Gjacquenot/simbody,chrisdembia/simbody,scamille/simbody,simbody/simbody