Fix partial fun notation

I had the temerity to push first the ()-free version of Erlang's grammar.
I shouldn't have as it exhibited unnatural syntax usage, and syntax should be as strict as possible in order to be readable best.

This patch disables greediness of the partial fun notation, so that `fun a:b(c)/3(d)/2` is not parsed as a partial fun with `c` and `d` as first arguments and 2 missing ones.
Instead it is a list of expressions (`fun a:b(c)/3` & `(d)/2`) in a **seqExprs** context, or a parse error outside it.

Here's a special factorial func showing the partial fun notation along the use of operator `:`
```haskell
factorial' /1 =
  fun
    (f ) -> fun :/1
    (f') -> fun :()/1
    (0) -> 1
    (N) when N > 0 -> N * :(N -1)
    (f24) -> fun :(4)/0
    (___) ->     :(4)
  end
```

This fixes https://github.com/fenollp/kju/issues/8.