Fix [3484066] Compilation error in Visual Studio 2011 Preview

git-svn-id: https://assimp.svn.sourceforge.net/svnroot/assimp/trunk@1159 67173fc5-114c-0410-ac8e-9d2fd5bffc1f

code/BlenderModifier.cpp

@@ -48,6 +48,8 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #include "SceneCombiner.h"
 #include "Subdivision.h"
 
+#include <functional>
+
 using namespace Assimp;
 using namespace Assimp::Blender;