Add test

Author: odersky

tests/neg-custom-args/captures/i15772.scala

@@ -0,0 +1,19 @@
+class C {
+   def bad() = println("I've gone bad!")
+}
+
+def newC: {*} C = C()
+
+type Observe[T] = (T => Unit) -> Unit
+def unsafe(cap: {*} C) = cap.bad()
+
+def box[T](v: T) : Observe[T] = {
+  (fn: T => Unit) => fn(v)
+}
+
+def main() : Int = {
+   val boxed : Observe[{*} C] = box(newC)
+   boxed(unsafe)
+
+   0
+}