[m-users.] Function to remove unicode byte order mark

[Dirk Ziegemeyer]

> Hi Dirk,
> 
> A slight improvement is to use the (in, in, uo) mode of first_char to
> avoid copying the rest of the string unless the first char is the BOM,
> 
>    first_char(S, '\xFEFF\', Rest)
> 
> Peter

Hi Peter,

thank you for this tip.

Dirk