v4 preprocessor: fixed minor memory leak

git-svn-id: https://www.dynare.org/svn/dynare/dynare_v4@1698 ac1d8469-bf42-47a9-8791-bf33cf982152

ParsingDriver.cc

@@ -75,6 +75,9 @@ ParsingDriver::parse(istream &in)
   Dynare::parser parser(*this);
   parser.parse();
 
+  if (location.begin.filename)
+    delete location.begin.filename;
+
   delete lexer;
   delete tmp_symbol_table;