Do not include headers if not necessary, use forward declarations instead

src/lua/LuaStack.cpp

@@ -26,6 +26,10 @@ OTHER DEALINGS IN THE SOFTWARE.
 
 #include "LuaStack.h"
 #include "Assert.h"
+#include "Vec2.h"
+#include "Vec3.h"
+#include "Mat4.h"
+#include "Quat.h"
 
 namespace crown
 {

src/lua/LuaStack.h

@@ -28,14 +28,15 @@ OTHER DEALINGS IN THE SOFTWARE.
 
 #include "lua.hpp"
 #include "Types.h"
-#include "Vec2.h"
-#include "Vec3.h"
-#include "Mat4.h"
-#include "Quat.h"
 
 namespace crown
 {
 
+class Vec2;
+class Vec3;
+class Mat4;
+class Quat;
+
 Vec2* next_vec2();
 Vec3* next_vec3();