TGLObject and subclasses

-----------------------------------------

Introduce new member 'Bool_t TGLObject::fMultiColor' that specifies
whether the class uses multiple colors for its rendering. This
information is important when drawing highlight or outlines around
objects as display-lists can not be used if color-state changes are
stored in them.

With this modification most of the logick for
  virtual Bool_t TGLLogicalShape::ShouldDLCache(...)
can be implemented in TGLObject version.

Most of the GL-rendering classes have been fixed to properly set the
fMultiColor state and rely on the TGLObject::ShouldDLCache().


TGLPhysicalShape
----------------

Use TGLLogicalShape::Draw() instead of DirectDraw() when drawing
highlights to allow usage of display-lists for classes that do not use
multiple colors.


TGLUtil
-------

Decrease the default draw-quality for DrawLine/Cylinder/Sphere/Disk to
10. With software rendering the previous value of 60 caused very low
refresh rates.

Introduce two inner classes TDrawQualityModifier and
TDrawQualityScaler allowing easy/safe modification of draw-quality for
the above functions.

Introduce inner class TColorLocker allowing easy/safe modification of
color-lock state.


git-svn-id: http://root.cern.ch/svn/root/trunk@24214 27541ba8-7e3a-0410-8455-c3a389f83636