* preprocessor: make optional the warnings about uninitialized...

* preprocessor: make optional the warnings about uninitialized parameters/endogenous/exogenous, added a new "warn_uninit" option to dynare command to display them
* reference manual: documented the new option, fixed XML conformance of the document


git-svn-id: https://www.dynare.org/svn/dynare/trunk@3135 ac1d8469-bf42-47a9-8791-bf33cf982152