- Support for 2D graphical Cuts for TClonesArray members
  - Support for 1D graphical Cuts by using their X minimum and
        maximum as ( Xmin <= Formula <= Xmax ).

  - Support for the following TTreeFormula special functions.

        Entry$   : return the current entry number (== TTree::GetReadEntry())
        Entries$ : return the total number of entries (== TTree::GetEntries())
        Length$  : return the total number of element of this formula for this
                        entry (==TTreeFormula::GetNdata())
        Iteration$: return the current iteration over this formula for this
                        entry (i.e. varies from 0 to LENGTH$).

  - Synchronization of the dimensions of all the formulas involved in
        a Draw call.

    For example for (with fMatrix[4][4] and fTracks[fNtrack].fVertex[3]
      T->Draw("fMatrix","fVertex>=2");

    The corrected result is histogram use something like:

        if (fTracks[0].fVertex[0]>=2) fMatrix[0][0];
        if (fTracks[0].fVertex[1]>=2) fMatrix[0][1];
        if (fTracks[0].fVertex[2]>=2) fMatrix[0][2];
        if (fTracks[1].fVertex[0]>=2) fMatrix[1][0];
        if (fTracks[1].fVertex[1]>=2) fMatrix[1][1];
        if (fTracks[1].fVertex[2]>=2) fMatrix[1][2];
        ....

    The old behavior was:

        if (fTracks[0].fVertex[0]>=2) fMatrix[0][0];
        if (fTracks[0].fVertex[1]>=2) fMatrix[0][1];
        if (fTracks[0].fVertex[2]>=2) fMatrix[0][2];
        if (fTracks[1].fVertex[0]>=2) fMatrix[0][3]; // note the extra step here.
        if (fTracks[1].fVertex[1]>=2) fMatrix[1][0];
        if (fTracks[1].fVertex[2]>=2) fMatrix[1][1];
        ....


git-svn-id: http://root.cern.ch/svn/root/trunk@4242 27541ba8-7e3a-0410-8455-c3a389f83636