small extension to `...` notation

[Stefan Holdermans]

Ben,

>>>  xs `zipWith (+)` ys

> Another problem is that it's not clear how to declare the fixity of  
> these things. Should they always have the default fixity? Should  
> they be required to have the form `<ident> <args>` and use the  
> fixity of `ident`? Neither approach seems very clean.

Following Philippa's suggestion to handle nesting, one could again  
treat `<ident>` and `<non-indent-expr>` differently and always assume  
the latter is given infix 9.

Regards,

   Stefan