Add test case

Author: odersky

tests/run/mixins1/A_1.scala

@@ -0,0 +1,11 @@
+trait A {
+
+  var x = 3
+  println("hi")
+  val y = x * x
+
+  def f: Int = x + y
+
+  def f(z: Int): Int = f + z
+
+}

tests/run/mixins1/C_2.scala

@@ -0,0 +1,12 @@
+// Intended to be compiled with either 2.11 or 2.12
+class C extends A {
+  x = 4
+
+  override def f: Int = super.f
+
+  val z = x + f(x) + y
+}
+
+object Test extends App {
+  new C().f
+}