In TH2, TH2, TH3 add support for SetBuffer when one of the lower limits

is greater or equal to the upper limit.

In TProfile2D constructors force an additional call to SetBuffer.
Because SetBuffer is called from the TH2 constructors, TH1::setBuffer
was called instead of TProfile2D::SetBuffer.

Fix a bug in TProfile2D::BufferEmpty.


git-svn-id: http://root.cern.ch/svn/root/trunk@11012 27541ba8-7e3a-0410-8455-c3a389f83636