estimated_params: check that no symbol is declared twice in the block

Closes #296
Remove unused options_.verbosity
Reorganization of warnings

 - at the end of the computation, don't display all preprocessor warnings but
   only their number
 - also display if there has been a MATLAB/Octave warning (counting their
   number does not seem feasible). Closes #181
 - add new "nowarn" option to disable all warnings. Closes #301
reporting (WIP)
Remove obsolete workaround for Octave 3.2
Revert "Remove unused options_.verbosity"

This reverts commit cacb0470f8d72c1c99728452df6d8a3f852b57e1.

It was making bytecode crashing. This field will still have to be removed later
when dealing with #295.
Bugfix in PosteriorIRFs

Fixed ancient copy and paste mistake from stoch_simul for relative IRFs
in Posterior IRFs
Merge pull request #305 from JohannesPfeifer/master

Bugfix in Posterior IRFs
Deleting redundant line and initializing arrays

Deleted redundant global statement and initialized arrays used
Merge pull request #311 from JohannesPfeifer/master

Speeding up of forecasting, cosmetic change
Fix bug introduced in ae82c28
Remove obsolete section about smoother on calibrated models.

We now have the `calib_smoother' command.
Remove spurious display when there is zero preprocessor warning
Remove unused field n_exog of DynamicModelDLL class
Construct the filename of the dynamic MEX file only at the deepest level

In the calling chain, only pass the basename of the MOD file.
Implementation of steady state computation in estim DLL, using the GSL

Does not seem very robust (fails on fs2000), need to investigate why.
Start refactoring of penalty handling

Handle all events that lead to a penalty through an exception.
Next steps:
- make all exceptions derive from a common class containing info code and
  penalty value
- catch these exceptions at the top-level, and construct the penalty-adjusted
  likelihood
reporting (WIP)
More explicit error message when posterior mode file is outdated
oo_.PosteriorTheoreticalMoments.correlation contains autocorrelations