[Man] Add info about xrdfs query stats
[XrdCl] Improce the help message about xrdfs query stats
[XrdCl] Add PrefName OpenFlags
[XrdCl] Add xrdfs locate -m and document locate parameters
[Man] Add info about xrdfs stat -m
[XrdXrootd] Make kXR_dirlist+kXR_dstat response conform to the spec
[XrdCl] Parse kXR_dirlist+kXR_dstat
[XrdCl] Prevent FileSystem::DirList from issuing stats if the stat info is already provided by bulk dirlist