JS backend: added identityEquals support.

js/js.translator/testFiles/expression/identityEquals/cases/identityEqualsMethod.kt

@@ -0,0 +1,21 @@
+package foo
+
+class X
+
+fun box(): String {
+    val a = X()
+    val b = X()
+    if (!a.identityEquals(a)) return "a !== a"
+    if (a.identityEquals(b)) return "X() === X()"
+    val c = a
+    if (!c.identityEquals(a)) return "c = a; c !== a"
+
+    if (X() identityEquals a) return "X() identityEquals a"
+
+    val t = !(X() identityEquals a)
+    if (!t) return "t = !(X() identityEquals a); t == false"
+
+    val f = !!(X() identityEquals a)
+    if (f) return "f = !!(X() identityEquals null); f == true"
+    return "OK";
+}

js/js.translator/testFiles/expression/identityEquals/cases/identityEqualsMethodForPrimitives.kt

@@ -0,0 +1,14 @@
+package foo
+
+fun box(): String {
+    if (!null.identityEquals(null)) return "null !== null"
+    if (!("ab" identityEquals "ab")) return "ab !== ab"
+    if (("ab" identityEquals "a")) return "ab === a"
+
+    if ("0" identityEquals 0) return "'0' === 0"
+    if (!(0 identityEquals 0)) return "0 !== 0"
+    if (0 identityEquals 1) return "0 === 1"
+
+
+    return "OK";
+}