Introduced the "slice_closing_radius" to define, how large gaps

will be closed after triangle mesh slicing.
The value is set to 0.049 by default, which corresponds to the hard
coded default in Slic3r-1.41.3.

See issues #520 #820 #1029 #1364 for the reference of why we need
the parameter for being able to print some specific models.

src/libslic3r/SLA/SLASupportTree.cpp

@@ -2105,7 +2105,7 @@ SlicedSupports SLASupportTree::slice(float layerh, float init_layerh) const
     fullmesh.merge(get_pad());
     TriangleMeshSlicer slicer(&fullmesh);
     SlicedSupports ret;
-    slicer.slice(heights, &ret, get().ctl().cancelfn);
+    slicer.slice(heights, 0.f, &ret, get().ctl().cancelfn);
 
     return ret;
 }