Replace the trunk code that uses the deprecated TH1::kCanRebin bit with
the new methods TH1::CanExtendAllAxes() and TH1::SetCanExtend() - see r47909,
r48012 and r48031. The old TH1::kCanRebin bit did not really have much to
do with histogram rebinning, but rather with extending the limits of the
histogram's axes (which can cause a rebin, but only in some cases). As such,
the word "Rebin" has been replaced with "Extend" for the new methods.

Rename TH1::RebinAxis() to TH1::ExtendAxis() for the reasons stated above.
The TH1::RebinAxis() method will be kept in v6-00 for backward compatibility
with an obsolete warning and will be removed in v6-02. The current
implementation simply forwards the call to TH1::ExtendAxis().


git-svn-id: http://root.cern.ch/svn/root/trunk@48046 27541ba8-7e3a-0410-8455-c3a389f83636