egs_view: track view now faster, can handle clipping planes

Memory usage is also significantly decreased, as all vertices are grouped
together in large arrays, and the loading step now eliminates many redundant
vertices.

In the process of making these changes, I modified a method of EGS_Vector
to be a const reference, like all the others.

HEN_HOUSE/egs++/egs_vector.h

@@ -83,7 +83,7 @@ class EGS_EXPORT EGS_Vector {
  return *this;
  };
 
- // EGS_Vector substractions
+ // EGS_Vector subtractions
  //
  EGS_Vector operator-(const EGS_Vector &v) const {
  return EGS_Vector(x-v.x,y-v.y,z-v.z);
@@ -106,7 +106,7 @@ class EGS_EXPORT EGS_Vector {
  z *= f;
  return *this;
  };
- friend EGS_Vector operator*(EGS_Float f, EGS_Vector &v) {
+ friend EGS_Vector operator*(EGS_Float f, const EGS_Vector &v) {
  return v*f;
  };
  EGS_Float operator*(const EGS_Vector &v) const {