'mod' and 'div' need brackets ro read as atoms

[Jasper Taylor]

| ?- P = div.
uncaught exception: error(syntax_error('user_input:1 (char:5) current or 
previous operator needs brackets'),read_term/3)

This is a problem because I cannot read terms written by pre-1.4 
versions of GNU prolog (or other prologs) including these atoms. Also 
there does not seem to be any reason for it -- other 2-ary arithmetic 
operators like atan2 can be read directly so why not these?
    --Jasper