- In ComputeZ: Wrong zeros may appeared when points sit on a regular grid.   This problem is now fixed. It showed when a TGraph2D was plotted with option   "surf1" for instance. Some peaks were visible in random places on the   surface.
- In ComputeZ: Wrong zeros may appeared when points sit on a regular grid.
  This problem is now fixed. It showed when a TGraph2D was plotted with option
  "surf1" for instance. Some peaks were visible in random places on the
  surface.


git-svn-id: ecbadac9c76e8cf640a0bca86f6bd796c98521e3@15292 27541ba8-7e3a-0410-8455-c3a389f83636

dawehner/root,bbannier/ROOT,dawehner/root,bbannier/ROOT,dawehner/root,dawehner/root,dawehner/root,bbannier/ROOT,bbannier/ROOT,bbannier/ROOT,bbannier/ROOT,dawehner/root,dawehner/root,dawehner/root,bbannier/ROOT