These could lead to undefined behaviour if e.g. a negative value from ftell
was used to allocate memory.
Also store result of ftell in a long;
The result may previously have been truncated on some platforms
This adds the ability for geometry sets to store build settings that can
be automatically applied when they are loaded. This should allow sharing
of .gset files to demonstrate problems with certain settings on certain
files. It also allows people to diagnose problems more easily by being
able to dump their own triangle meshes and settings and load them in the
demo, with all of its visualization options. .gset files can be created
from the current mesh and settings by pressing the 9 key, which will
generate it in the same folder as the input mesh.
Also converts more of the demo to use STL.
