mtlb_uint64 Matlab uint64 emulation function

## Description

Matlab and Scilab `uint64` behave differently :

- Beyong the main interval bounds, Scilab's `uint64()` wraps, while Matlab's `mtlb_uint64()` saturates.
- For non integer values, Scilab's `uint64()` truncates the fractional part, while Matlab's `mtlb_uint64()` rounds to the nearest integer.

Let `imax = 2^64 - 1 = 18 446 744 073 709 551 615`.

x | uint64(x) | mtlb_uint64(x)
--- | --- | ---
%nan | 0 | 0
-%inf | 0 | 0
-2 | imax-1 | 0
-1 | imax | 0
0 | 0 | 0
1 | 1 | 1
10.2 | 10 | 10
10.5 | 10 | 11
10.51 | 10 | 11
... | ... | ...
imax | imax | imax
imax+1 | 0 | imax
imax+1 | 1 | imax
%inf | imax | imax

`mtlb_uint64` has not to be used for hand coded functions.

The function `mtlb_uint64(A)` is used by `mfile2sci` to replace `uint64(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.