New utility class IGeoPolygon from Mihaela Gheata:

  It is able to locate if a point is inside/outside an arbitrary polygon,
defined by vertices in the XY plane - possibly scaled/translated. It
will be used by the class TGeoXtru (extruded polygon) to come soon.


git-svn-id: http://root.cern.ch/svn/root/trunk@7951 27541ba8-7e3a-0410-8455-c3a389f83636