Move other lone thirdparty files to thirdparty/misc

Also move Box2D ConvexDecomposition contrib code to
thirdparty/b2d_convexdecomp.

scene/resources/surface_tool.h

@@ -30,9 +30,10 @@
 #ifndef SURFACE_TOOL_H
 #define SURFACE_TOOL_H
 
-#include "mikktspace.h"
 #include "scene/resources/mesh.h"
 
+#include "thirdparty/misc/mikktspace.h"
+
 class SurfaceTool : public Reference {
 
 	GDCLASS(SurfaceTool, Reference);