Symmetric coroutines!

test/fiber/run_with_value_direct_reenter.wren

@@ -0,0 +1,10 @@
+var fiber
+
+fiber = new Fiber {
+  IO.print(1) // expect: 1
+  fiber.run("ignored")
+  IO.print(2) // expect: 2
+}
+
+fiber.call
+IO.print(3) // expect: 3