mtlb_true Matlab true emulation function

## Description

There is no Scilab equivalent for Matlab `true`. However, Scilab `ones` returns a result interpreted in an equivalent way for Scilab.

Matlab `true` and Scilab `ones` behave differently in some particular cases:

- With a scalar input: Matlab `true` returns a n x n matrix of ones while Scilab `ones` returns a 1.

The function `mtlb_true(A)` is used by `mfile2sci` to replace `true(A)` when it was not possible to know what was the input while porting Matlab code to Scilab. This function will determine the correct semantic at run time. If you want to have a more efficient code it is possible to replace `mtlb_true` calls:

- If `A` is a scalar `mtlb_true(A)` may be replaced by `ones(A,A)`

- If `A` is not a scalar `mtlb_true(A)` may be replaced by `ones(A)`

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