JS backend: add support multi declaration

js/js.translator/testFiles/multideclaration/cases/multiValInIntRangeFor.kt

@@ -0,0 +1,22 @@
+package foo
+
+fun Int.component1() : Int {
+    return this + 10;
+}
+
+fun Int.component2() : String = "b"
+
+fun box(): String {
+    var i = 0;
+    var s = "";
+    val range = 1..4
+    for ((a, b) in range) {
+        i = a
+        s = b
+    }
+
+    if (i != 14) return "i != 14, it: $i"
+    if (s != "b") return "s != 'b', it: $s"
+
+    return "OK"
+}