+ changes to support "cluster ads" (classad chainging in the schedd).
+ changes to support "cluster ads" (classad chainging in the schedd).

+ file to check for access with the schedd are now kept in a hashtable
instead of a ExtArray.  so on a cluster with 800 jobs, we no longer ask
the schedd to stat this file 800 times.  just once is fine.  :^)

+ don't check /dev/null for permissions.

+ don't call calc_image_size() over & over on the same executable

mambelli/osg-bosco-marco,htcondor/htcondor,djw8605/htcondor,zhangzhehust/htcondor,clalancette/condor-dcloud,neurodebian/htcondor,clalancette/condor-dcloud,djw8605/htcondor,mambelli/osg-bosco-marco,zhangzhehust/htcondor,djw8605/condor,htcondor/htcondor,djw8605/condor,zhangzhehust/htcondor,djw8605/htcondor,clalancette/condor-dcloud,neurodebian/htcondor,htcondor/htcondor,djw8605/htcondor,djw8605/condor,clalancette/condor-dcloud,neurodebian/htcondor,bbockelm/condor-network-accounting,clalancette/condor-dcloud,djw8605/condor,djw8605/htcondor,mambelli/osg-bosco-marco,djw8605/condor,djw8605/htcondor,neurodebian/htcondor,zhangzhehust/htcondor,bbockelm/condor-network-accounting,neurodebian/htcondor,neurodebian/htcondor,djw8605/condor,djw8605/condor,clalancette/condor-dcloud,mambelli/osg-bosco-marco,zhangzhehust/htcondor,bbockelm/condor-network-accounting,zhangzhehust/htcondor,mambelli/osg-bosco-marco,bbockelm/condor-network-accounting,bbockelm/condor-network-accounting,djw8605/htcondor,htcondor/htcondor,mambelli/osg-bosco-marco,neurodebian/htcondor,neurodebian/htcondor,zhangzhehust/htcondor,djw8605/condor,zhangzhehust/htcondor,clalancette/condor-dcloud,htcondor/htcondor,htcondor/htcondor,bbockelm/condor-network-accounting,bbockelm/condor-network-accounting,zhangzhehust/htcondor,bbockelm/condor-network-accounting,djw8605/htcondor,djw8605/htcondor,htcondor/htcondor,mambelli/osg-bosco-marco,mambelli/osg-bosco-marco,neurodebian/htcondor,htcondor/htcondor