- Fix https://savannah.cern.ch/bugs/?30595 . The loop on the ComputeRange    methods (called for each graph in the multigraph) returned the last values    provided by the last call to ComputeRange instead of computing the minimum   and maximum of all of them. Revision 20335 introduced this bug.
- Fix https://savannah.cern.ch/bugs/?30595 . The loop on the ComputeRange 
  methods (called for each graph in the multigraph) returned the last values 
  provided by the last call to ComputeRange instead of computing the minimum
  and maximum of all of them. Revision 20335 introduced this bug.


git-svn-id: ecbadac9c76e8cf640a0bca86f6bd796c98521e3@20433 27541ba8-7e3a-0410-8455-c3a389f83636

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