mtlb_dir Matlab dir emulation function

## Description

Matlab and Scilab `dir` behave differently:

- When result is stored in a variable: Matlab `dir` returns a structure but Scilab `dir` returns a 'dir' tlist, so data can not be extracted in the same way.

The function `mtlb_dir([path])` is used by `mfile2sci` to replace `dir([path])` when output is stored in a variable. There is no replacement possibility for it, else (when `mtlb_dir` is replaced by `dir`) data can not be extracted like in Matlab. For example, Scilab equivalent for Matlab `L=dir;file_name=L(1).name;` is `L=dir();file_name=L.name(1);`.

Caution: `mtlb_dir` has not to be used for hand coded functions.