Document treatment of several Matlab statements in one line

If Dynare encounters an unknown expression at the beginning of a line or after a semicolon, it will parse the rest of that line as native Matlab code, even if there are more statements separated by semicolons present.

This explanation does not cover the case of the `.mod` file in #1637 where the "Matlab code" comes after a semicolon on a line. What do you think about this? In fact, do we mention anywhere else in the manual that Dynare passes Matlab code directly into the driver file? Does that need to be addressed too? ``` If Dynare encounters an unknown expression at the beginning of a line or after a semicolon, it will parse the rest of that line as native Matlab code, even if there are more statements separated by semicolons present. ```

How about the updated version at https://git.dynare.org/JohannesPfeifer/dynare/commit/20b51b3c0815e8ad1a87ff097c7e6eb1fab34c85