JS tests: added tests for dynamic.

js/js.translator/testData/dynamic/cases/operationsWithAssignment.kt

@@ -0,0 +1,25 @@
+package foo
+
+fun box(): String {
+    var a: dynamic = 12
+    var b: dynamic = 33.4
+    var c: dynamic = "text"
+    val d: dynamic = true
+
+    a += d
+    assertEquals(13, a)
+    c += a
+    assertEquals("text13", c)
+    a %= 7
+    assertEquals(6, a)
+    b -= 32
+    assertEquals(1.3999999999999986, b)
+    b *= n
+    assertEquals(58.79999999999994, b)
+    b /= a
+    assertEquals(9.79999999999999, b)
+    c += a * 3 + b / n
+    assertEquals("text1318.233333333333334", c)
+
+    return "OK"
+}