Add test case

Tests #518.

Author: odersky

tests/pos/i518.scala

@@ -0,0 +1,6 @@
+class Meter(val underlying: Int) extends AnyVal
+
+class Test {
+  val x: Int = new Meter(3).hashCode()
+   // After phase VCInline the rhs should be expanded to Meter.hashCode$extension(3)
+}