Added note to ForEach.h of VS2008 incompatibility.

Source/Engine/Container/ForEach.h

@@ -2,6 +2,8 @@
 
 #include "Vector.h"
 
+// Note: ForEach is not supported on all compilers, such as VS2008.
+
 namespace Urho3D {
 
 template<typename T>