Rename extlibs to thirdparty

thirdparty/include/chipmunk/cpRobust.h

@@ -0,0 +1,11 @@
+#include "chipmunk/cpVect.h"
+
+// This is a private header for functions (currently just one) that need strict floating point results.
+// It was easier to put this in it's own file than to fiddle with 4 different compiler specific pragmas or attributes.
+// "Fast math" should be disabled here.
+
+// Check if c is to the left of segment (a, b).
+cpBool cpCheckPointGreater(const cpVect a, const cpVect b, const cpVect c);
+
+// Check if p is behind one of v0 or v1 on axis n.
+cpBool cpCheckAxis(cpVect v0, cpVect v1, cpVect p, cpVect n);