JS Back-end does not handle complex patterns any more

#KT-2359 In Progress

js/js.translator/testFiles/patternMatching/cases/multipleCases.kt

@@ -5,12 +5,12 @@ fun box() : Int {
   val d = 5
   var z = 0
   when(c) {
-    is 5, is 3 -> z++;
+    5, 3 -> z++;
     else -> {z = -1000;}
   }
 
   when(d) {
-    is 5, is 3 -> z++;
+    5, 3 -> z++;
     else -> {z = -1000;}
   }
   return z

js/js.translator/testFiles/patternMatching/cases/whenAsExpression.kt

@@ -4,8 +4,8 @@ package foo
 fun box() : Boolean {
 
     return (when(1) {
-        is 2 -> 3
-        is 1 -> 1
+        2 -> 3
+        1 -> 1
         else -> 5
     } == 1)
 

js/js.translator/testFiles/patternMatching/cases/whenNotValue.kt

@@ -1,11 +0,0 @@
-package foo
-
-fun box() : Boolean {
-  var a = 4
-  when(a) {
-    !is 3 -> {a = 10;}
-    !is 4 -> {a = 20;}
-    else -> {a = 30;}
-  }
-  return (a == 10)
-}

js/js.translator/testFiles/patternMatching/cases/whenValue.kt

@@ -3,8 +3,8 @@ package foo
 fun box() : Boolean {
   var a = 4
   when(a) {
-    is 3 -> {a = 10;}
-    is 4 -> {a = 20;}
+    3 -> {a = 10;}
+    4 -> {a = 20;}
     else -> {a = 30;}
   }
   return (a == 20)

js/js.translator/testFiles/patternMatching/cases/whenValueOrType.kt

@@ -13,13 +13,13 @@ fun box() : Boolean {
   var a = A() : Any?
   var b = null : Any?
   when(a) {
-    is null -> c = 10;
+    null -> c = 10;
     is B -> c = 10000
     is A  -> c = 20;
     else -> c = 1000
   }
   when(b) {
-    is null -> c += 5
+    null -> c += 5
     is B -> c += 100
     else -> c = 1000
   }