Fix other tests

Author: phischu

examples/stdlib/io/filesystem/async_file_io.effekt

@@ -1,6 +1,7 @@
 import io
 import io/error
 import io/filesystem
+import io/promise
 
 def program(path1: String, path2: String) =  {
   val f1 = promise(box {

examples/stdlib/io/time.effekt

@@ -1,18 +1,19 @@
 import io
 import io/time
+import io/promise
 
 def main() = {
 
   val p1 = promise(box {
     println("Start p1");
-    wait(250)
+    sleep(250)
     println("Stop p1");
     1
   })
 
   val p2 = promise(box {
     println("Start p2");
-    wait(150)
+    sleep(150)
     println("Stop p2");
     2
   })