Add entry kRecovered in TFile enum.

The bit kRecovered is set when Recover has been called on the file.
A user can test if the file has been recovered with
  file->TestBit(TFile::kRecovered);


git-svn-id: http://root.cern.ch/svn/root/trunk@5418 27541ba8-7e3a-0410-8455-c3a389f83636