Using the xroot dir interface for a directory listing command

xroot_clients/CMakeLists.txt

xroot_clients/CTADirCmd.cpp

xroot_clients/CTADirCmd.hpp

xroot_clients/CTADirCmdMain.cpp

xroot_plugins/CMakeLists.txt

xroot_plugins/XrdProDir.cpp

xroot_plugins/XrdProDir.hpp

xroot_plugins/XrdProFilesystem.cpp