Add test file

Author: Antoine Brunner

tests/run-bootstrapped/iarray-extmtds.check

@@ -0,0 +1 @@
+IArray(1,2)

tests/run-bootstrapped/iarray-extmtds.scala

@@ -0,0 +1,5 @@
+
+object Test extends App {
+  val arr = IArray[Int](1, 2, 3)
+  println(arr.take(2))
+}