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/SLABasePool.cpp

@@ -561,7 +561,7 @@ void base_plate(const TriangleMesh &mesh, ExPolygons &output, float h,
         heights.emplace_back(hi);
 
     std::vector<ExPolygons> out; out.reserve(size_t(std::ceil(h/layerh)));
-    slicer.slice(heights, &out, thrfn);
+    slicer.slice(heights, 0.f, &out, thrfn);
 
     size_t count = 0; for(auto& o : out) count += o.size();