aaply patch from Andrei to have a lazy allocation of the TArray[x] of histograms and profiles.

The allocation is done only if a SetBinContent() or AddBinContent() is called.
This feature can be activated via the static TH1::SetLazyAllocation(kTRUE)


git-svn-id: http://root.cern.ch/svn/root/trunk@40319 27541ba8-7e3a-0410-8455-c3a389f83636