Add max visible lights info and cycling menu option

Display the maximum of simultaneously visible light on the info
screen, allow cycling this number with F8.

Signed-off-by: Harm Hanemaaijer <fgenfb@yahoo.com>
Several changes; improve shadow volume, billboard drawing, and more

Improvements to compound model handling and its utilization in demo1.

Allow use of triangle fans or triangle stips for stencil shadow volumes.
Triangle fans can often be used for direction light shadow volumes and
require less space on the GPU and should be faster. This requires
closed, regular models, and a few model flags have been added to avoid
failed attempts to construct a triangle fan. For point source lights,
a triangle strip can be used when the GPU supports "primitive restart";
this results in a small saving of space on the GPU (five instead of
six indices per pair of shadow volume side triangles).

Improve shadow cache statistics, including total vertex count, and
add GUI keyboard toggles for more shadow cache settings.

Code has been added to be more elaborately reduce geometry when
calculating edges (for example when blocky objects are combined in a
compound object), taking advantage of the existing polygon
reduction function, with the goal of further reducing shadow volumes
(with increased use of triangle fans) but this is work in progress
and disabled.

Fix bug in InsertPolygonVertex used with geometry preprocessing,
which caused texture coordinate and color data not to be updated.

Reorganize and fix/improve particle system/billboard handling, including
changes to the model and object class flags. Single billboards are drawn
using a triangle fan with two triangles. Halos and particle systems
consisting of halos are drawn with the same shader. Standard billboards
are now more fully supported, with emission color and map with
transparency, but untested. Particle systems with billboards are also
supported.

Remove unused shader source files. Reformat the file sreVectorMath.h
to remove CR at line endings.

Signed-off-by: Harm Hanemaaijer <fgenfb@yahoo.com>