Patches from Archlinux.

http://bugs.gentoo.org/show_bug.cgi?id=366073
--- a/src/celmath/intersect.h
+++ b/src/celmath/intersect.h
@@ -15,6 +15,7 @@
 #include "ray.h"
 #include "sphere.h"
 #include "ellipsoid.h"
+#include "mathlib.h"
 
 
 template<class T> bool testIntersection(const Ray3<T>& ray,
--- a/src/celengine/frametree.h
+++ b/src/celengine/frametree.h
@@ -14,6 +14,7 @@
 #define _CELENGINE_FRAMETREE_H_
 
 #include <vector>
+#include <cstddef>
 
 class Star;
 class Body;