allow line break at operators

[Ethan Furman]

Chris Angelico wrote:
> Incidentally, in the original expression, it would be slightly more
> sane to write it as:
> 
> a = x + y) * z
> 
> borrowing from the musical concept that a repeat sign with no
> corresponding begin-repeat means to repeat from the beginning. But
> both of these violate XKCD 859.

Argh!  ;)

~Ethan~