Refactor folder (#10475)

Move many third-party components' source codes from the src folder to a new folder called deps_src. The goal is to make the code structure clearer and easier to navigate.

deps_src/clipper/clipper_z.cpp

@@ -0,0 +1,7 @@
+// Hackish wrapper around the ClipperLib library to compile the Clipper library with the Z support.
+
+// Enable the Z coordinate support.
+#define CLIPPERLIB_USE_XYZ
+
+// and let it compile
+#include "clipper.cpp"