preprocessor: replace exit(1) with exit(EXIT_FAILURE)

ComputingTasks.cc

 /*
- * Copyright (C) 2003-2016 Dynare Team
+ * Copyright (C) 2003-2017 Dynare Team
  *
  * This file is part of Dynare.
  *
@@ -336,7 +336,7 @@ RamseyConstraintsStatement::writeOutput(ostream &output, const string &basename,
 	  break;
 	default:
 	  cerr << "Ramsey constraints: this shouldn't happen." << endl;
-	  exit(1);
+	  exit(EXIT_FAILURE);
 	}
       output << "', '";
       it->expression->writeOutput(output);

DynamicModel.cc

@@ -5012,7 +5012,7 @@ DynamicModel::writeFirstDerivativesC_csr(const string &basename, bool cuda) cons
 	  break;
 	default:
 	  std::cerr << "This case shouldn't happen" << std::endl;
-	  exit(1);
+	  exit(EXIT_FAILURE);
 	}
       derivative deriv(col_id + eq*cols_nbr,col_id,eq,it->second);
       D.push_back(deriv);