Fix memory leak in Xml document destructor. Thanks to Kevin Xu for helping me find this.
Fix memory leak in Xml document destructor. Thanks to Kevin Xu for helping me find this.

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