Build system:

* added flags "--disable-matlab" and "--disable-octave" to top-level configure script, to manually disable building of MEX files for MATLAB / Octave
* incorporated new conditional variance decomposition test to testsuite


git-svn-id: https://www.dynare.org/svn/dynare/trunk@3115 ac1d8469-bf42-47a9-8791-bf33cf982152