Read matlab mat files using matio library

I don't have access to the MatlabIO library, so I have attempted to read mat files using the open source matio library. This is almost working but there are problems in FileStorageModel.cpp:

```
./ModelTransfer test7.mat ../../matlab/Demo_model.xml
-------------------------------
        Model Transfer         
-------------------------------

deserializing Matlab (.mat) model...
converting...
serializing to OpenCV (.xml) model...
OpenCV Error: Bad argument (An attempt to add element without a key to a map, or add element with key to sequence) in icvXMLWriteTag, file /build/buildd/opencv-2.3.1/modules/core/src/persistence.cpp, line 2229
terminate called after throwing an instance of 'cv::Exception'
  what():  /build/buildd/opencv-2.3.1/modules/core/src/persistence.cpp:2229: error: (-5) An attempt to add element without a key to a map, or add element with key to sequence in function icvXMLWriteTag

Aborted
```
This might be caused by my old version of OpenCV or a bug someone else. As far as I can tell, the mat file is correctly read into memory but I could really do with a known "good" mat file the correctly converts in ModelTransfer with MatlabIO enabled. Anyone?

Note that matio only reads matlab files and does not read Octave mat files in the default mode (however Octave can save in a matlab format)