TGLFontManager:
Add utility function GetFontSize().

TEveCaloData:
Fix wrong usage of THStack.

TEveCalo, TEveCaloLegoEditor:
Remove obsolete memeber.

TEveLegoOverlay, LinkDef:
New class.

TEveCaloLegoGL:
Draw a semi-transparent plane parallel to the grid and have an
interactive marker on the scale which a user can drag to cause the
plane to move.

cms_calo.C:
Add overlay to the GL scene.


git-svn-id: http://root.cern.ch/svn/root/trunk@23868 27541ba8-7e3a-0410-8455-c3a389f83636