Avoid ambiguous overload on JDK 9

The addition of this method in `CharBuffer`

   CharBuffer position(int newPosition)

renders an ambiguity in:

```
scala> (b: java.nio.CharBuffer) => b.position
<console>:12: error: ambiguous reference to overloaded definition,
both method position in class CharBuffer of type (x$1: Int)java.nio.CharBuffer
and  method position in class Buffer of type ()Int
match expected type ?
       (b: java.nio.CharBuffer) => b.position
```

Manually applying the empty params avoids this.

Author: retronym

src/repl/scala/tools/nsc/interpreter/Scripted.scala

@@ -331,7 +331,7 @@ class WriterOutputStream(writer: Writer) extends OutputStream {
     byteBuffer.flip()
     val result = decoder.decode(byteBuffer, charBuffer, /*eoi=*/ false)
     if (byteBuffer.remaining == 0) byteBuffer.clear()
-    if (charBuffer.position > 0) {
+    if (charBuffer.position() > 0) {
       charBuffer.flip()
       writer write charBuffer.toString
       charBuffer.clear()