Current Eigen Version 3.1.2 (05.11.2012)
Current Eigen Version 3.2.1 (26.02.2014) updated on 14/05/2014

To update the lib:
- download Eigen
- unzip it somewhere
- delete (in the filesystem) the content of the folder eigenlib/Eigen and eigenlib/unsupported
- copy the two folders 'Eigen' and 'unsupported' here 
- check the svn status, svn-add the new files and svn-remove the missing ones.
- update this file
- commit everything