Introduce possibility to rebin each axis individually
see https://savannah.cern.ch/bugs/?89628

Added a new bit in TAxis to tag an axis as alphanumeric 
(i.e. when it contains only labels)

fixed kDecimal problem. Put now as Bit 7 of TObject bits, instead of using TAxis::fBits2

Add new methods: 

  TH1::SetCanRebin() which can enable/disable rebinning for all axes or for each axis individually
  This will replace the TH1::kCanRebin bit which will be deprecated
 
  TH1::CanRebinAllAxes() added to provide the functionality of TestBit(TH1::kCanRebin)

inline some TAxis methods

update stressHistogram to use new methods SetCanRebin and CanRebin


git-svn-id: http://root.cern.ch/svn/root/trunk@47909 27541ba8-7e3a-0410-8455-c3a389f83636