Removed some unused code

- removed define USE_AABB_INDIRECT (which switched between old and new AABB implementation)
- removed define SLIC3R_SLA_NEEDS_WINDTREE (relied on igl and was not used anyway)
- new define SLIC3R_HOLE_RAYCASTER (hides currently unused code)
- slight include cleanup
- removed obsolete source file SupportTreeIGL.cpp

src/libslic3r/SLA/Common.hpp

@@ -7,12 +7,6 @@
 #include <functional>
 #include <Eigen/Geometry>
 
-//#include "SLASpatIndex.hpp"
-
-//#include <libslic3r/ExPolygon.hpp>
-//#include <libslic3r/TriangleMesh.hpp>
-
-// #define SLIC3R_SLA_NEEDS_WINDTREE
 
 namespace Slic3r {