line at the end of the error bars when option "e1p" is used.
The old algorithm computef the length as being proportional to the marker size.
The new algorithm, in addition, takes into account the "errorx" parameter
as given by gStyle->GetErrorx().


git-svn-id: http://root.cern.ch/svn/root/trunk@3227 27541ba8-7e3a-0410-8455-c3a389f83636