reference manual:

* for MATLAB 64-bit under Windows, indicate where to download the required MS Visual C++ runtime for MEX files
* added a few explanations on auxiliary variables
* fixed mode_compute option of estimation
* indicate that only first order supported by ramsey_policy


git-svn-id: https://www.dynare.org/svn/dynare/trunk@3238 ac1d8469-bf42-47a9-8791-bf33cf982152