Reworked polygon sampling for SLA auto support generation.

Conditional compilation of an igl winding number tree for SLA support generator, as it is not used as of now and initialization of the tree is expensive.
Fixed issue with passing the new SLA point definition to the back end and back to the UI.

src/libslic3r/SLA/SLASupportTree.cpp

@@ -552,14 +552,12 @@ enum { // For indexing Eigen vectors as v(X), v(Y), v(Z) instead of numbers
 
 PointSet to_point_set(const std::vector<SupportPoint> &v)
 {
-    PointSet ret(v.size(), 5);
+    PointSet ret(v.size(), 3);
     long i = 0;
     for(const SupportPoint& support_point : v) {
         ret.row(i)(0) = support_point.pos(0);
         ret.row(i)(1) = support_point.pos(1);
         ret.row(i)(2) = support_point.pos(2);
-        ret.row(i)(3) = support_point.head_front_radius;
-        ret.row(i)(4) = (float)support_point.is_new_island;
         ++i;
     }
     return ret;