Changed to a more canonical name of the spec file and update the url

git-svn-id: file:///p/condor/workspaces/vdt/svn/native/redhat/trunk/xrootd-voms-plugin@20229 4e558342-562e-0410-864c-e07659590f8c
Changed back the name of the spec file

git-svn-id: file:///p/condor/workspaces/vdt/svn/native/redhat/trunk/xrootd-voms-plugin@20237 4e558342-562e-0410-864c-e07659590f8c
Explicetely changed to require the xrootd4 libraries

git-svn-id: file:///p/condor/workspaces/vdt/svn/native/redhat/trunk/xrootd-voms-plugin@20239 4e558342-562e-0410-864c-e07659590f8c