From Andrei:

- new files TGeoOverlap.h/cxx in geompainter directory. Contains one
base class and 2 derived, describing overlaps. The CheckOverlaps()
methods in TGeoManager and TGeoVolume fills a list of these objects
which is held by TGeoManager class and appears in the browser as
"Illegal overlaps". The elements in this list are ordered according the
overlapping distance, big comes first and extrusions before node
overlaps. Double-clicking triggers drawing. Points in the
overlapping/extruding region are paint in red, while the 2 candidates in
bleu/green. The list of overlaps is dynamic and changes whenever a check
is done per volume.
- volumes with invalid shapes post a warning (see ATLAS)


git-svn-id: http://root.cern.ch/svn/root/trunk@6083 27541ba8-7e3a-0410-8455-c3a389f83636