From bertrand:

- Added new method TList *TSystem::GetVolumes(Option_t *opt)
  returning the list of hard drives on Windows when opt = "all"
  or the current hard drive when opt = "cur"
  the return type is a TList of TObjString's containing the drive letters,
  i.e: for drives C: G: H: K:. The TList must be deleted by the user.
- Implement the ability to browse available (mounted) drives on Windows.
- Added list of available (mounted) drives in TGFSCombobox on Windows.


git-svn-id: http://root.cern.ch/svn/root/trunk@23625 27541ba8-7e3a-0410-8455-c3a389f83636