4.0: merged changesets 2078, 2089 and 2090 from trunk

* new debug messages in dynare_solve.m
* solve_algo=2 exits immediately after failure to solve one block
* new solve_algo=4 with different way of dealing with badly scaled or nearly singular Jacobian
* solve_algo=0 fails if Matlab's Optimization Toolbox not present
* dynare_solve fails if solve_algo not in [0,1,2,3,4]


git-svn-id: https://www.dynare.org/svn/dynare/branches/4.0@2095 ac1d8469-bf42-47a9-8791-bf33cf982152