fix fitting of TGraphErrors with errors in x when errors are much smaller than x values.  Now the error is used as extimate of the scale for the derivative step size See http://root.cern.ch/phpBB3/viewtopic.php?f=3&t=13294&p=57038#p57038
fix fitting of TGraphErrors with errors in x when errors are much smaller than x values. 
Now the error is used as extimate of the scale for the derivative step size
See http://root.cern.ch/phpBB3/viewtopic.php?f=3&t=13294&p=57038#p57038


git-svn-id: ecbadac9c76e8cf640a0bca86f6bd796c98521e3@40635 27541ba8-7e3a-0410-8455-c3a389f83636

dawehner/root,dawehner/root,dawehner/root,dawehner/root,dawehner/root,dawehner/root,dawehner/root,dawehner/root