Support EEP37: Funs with names

R17 will [probably](http://erlang.org/pipermail/eeps/2013-September/000466.html) include [my implementation of EEP37](https://github.com/nox/otp/compare/erlang:maint...eep37) which allows expressions of the form:

``` erlang
fact() ->
    fun Fact(N) when N > 0 -> N * Fact(N - 1); Fact(0) -> 1 end
```

PropEr should be able to cope with these expressions. I would like to test this but I don't know which case I should extend.