JS: move expressions test to box tests

js/js.translator/testData/box/expression/function/loopClosure.kt

@@ -0,0 +1,20 @@
+package foo
+
+var b = 0
+
+fun loop(times: Int) {
+    var left = times
+    while (left > 0) {
+        val u = { value: Int ->
+            b = b + 1
+        }
+        u(left--)
+    }
+}
+
+fun box(): String {
+    loop(5)
+    if (b != 5) return "fail: $b"
+
+    return "OK"
+}