Use std.string.lineSplitter with std.array.Appender!string

[NonNull]

Disambiguate how ?

```
     import std.string, std.array;
     auto s = appender!string;
     // .......
     auto a = s.lineSplitter;
```

Error: template std.string.lineSplitter cannot deduce function 
from argument types !()(Appender!string), candidates are:

std.string.lineSplitter(Flag keepTerm = No.keepTerminator, 
Range)(Range r) if (hasSlicing!Range && hasLength!Range && 
isSomeChar!(ElementType!Range) && !isSomeString!Range)

std.string.lineSplitter(Flag keepTerm = No.keepTerminator, C)(C[] 
r) if (isSomeChar!C)