preprocessor

Before this commit, a dynare call such as
```
dynare <<mod file>> -Db=“A” -Da=@{b}
```
would not expand the value of `b` in `a` whereas
```
dynare <<mod file>> -Da=“A” -Db=@{a}
```
would expand the value of `a` into `b` because the arguments were stored in a map which printed the `@#define` statements in the .mod file in alphabetic order.