Added missing Linux header (cstddef).

Author: luciusDXL

TheForceEngine/TFE_Editor/LevelEditor/levelEditorHistory.cpp

@@ -6,6 +6,7 @@
 #include <assert.h>
 #include <algorithm>
 #include <cstring>
+#include <cstddef>
 
 using namespace TFE_Editor;