memory manager published at flipcode.com. This can be turned on
with the OSG_USE_MEMORY_MANGER option which then uses custom global
new and delete operators as well as provide osgNew and osgDelete macro's
which add ability to log line and file from which calls are made.
Updated osg,osgUtil,osgDB,osgText and osgPlugins/osg to use osgNew/osgDelete,
and fixed memory leaks highlighted by the new memory manager.
Renamed the osg::VisualsSettings to osg::DisplaySettings, and
osgUtil::VisualsRequirementsVisitor to osgUtil::DisplayRequirementsVisitor.
Added support for OSG_SCREEN_HEIGHT into osg::DisplaySettings, and added
a DisplaySettings* to the constructors of osg::SceneView and osg::Camera.
