This will make a number of things easier in the future, as well as (finally!)
avoiding the Id-smashing problem which has plagued developers for so long.
Boy, I'm glad we're not using sup anymore. This update would have been
insane otherwise.
arrange for that directory to get created by mtree. Also, process secure
directory after all the others, because the programs there may overlay
ones installed from the main part of the tree.
