mtlb_uint16 Matlab uint16 emulation function

## Description

Matlab and Scilab `uint16` behave differently :

- Beyong the main interval bounds, Scilab's `uint16()` wraps, while Matlab's `mtlb_uint16()` saturates.
- For non integer values, Scilab's `uint16()` truncates the fractional part, while Matlab's `mtlb_uint16()` rounds to the nearest integer.

x | uint16(x) | mtlb_uint16(x)
--- | --- | ---
%nan | 0 | 0
-%inf | 0 | 0
-2 | 65534 | 0
-1 | 65535 | 0
0 | 0 | 0
2 | 2 | 2
10.2 | 10 | 10
10.5 | 10 | 11
10.51 | 10 | 11
... | ... | ...
65535 | 65535 | 65535
65536 | 0 | 65535
65537 | 1 | 65535
%inf | 65535 | 65535

`mtlb_uint16` has not to be used for hand coded functions.

The function `mtlb_uint16(A)` is used by `mfile2sci` to replace `uint16(A)` when it is not possible to know what is the input while porting Matlab code to Scilab. This function then determines the correct semantic at run time.