Enable support of FBX 2011 (7100)

Why isn't FBX 2011 (7100) supported by assimp?
I want to know reasons why assimp does not support FBX 2011.
Because the FBX version of FBX 2011 is `7100` (`7.1.0`).
(I have read these issues: #45 and #93.)

In my environment, Ubuntu 12.04.03 LTS and g++ 4.6,  assimp could import 7 FBX 2011 files which exported by Maya 2012 and 3dsMax 2012 with no error.
Please consider this pull request.

```
 $ head example2011ascii.fbx
; FBX 7.1.0 project file
; Copyright (C) 1997-2010 Autodesk Inc. and/or its licensors.
; All rights reserved.
; ----------------------------------------------------

FBXHeaderExtension:  {
	FBXHeaderVersion: 1003
	FBXVersion: 7100
	CreationTimeStamp:  {
		Version: 1000
```