Regular modifier checker implemented (initial version). A set of tests fixed accordingly.

Most of modifier diagnostic is expressed by REDUNDANT_MODIFIER, INCOMPATIBLE_MODIFIERS, REPEATED_MODIFIER, WRONG_MODIFIER_TARGET, WRONG_MODIFIER_PARENT.
A set of modifier diagnostics is not in use now (but not deleted yet).

js/js.translator/testData/delegation/cases/delegation4.kt

@@ -1,11 +1,11 @@
 // This test was adapted from compiler/testData/codegen/box/classes
 package foo
 
-open trait First {
+interface First {
     public open fun foo(): Int
 }
 
-open trait Second : First {
+interface Second : First {
     public open fun bar(): Int
 }
 

js/js.translator/testData/inlineMultiFile/cases/use/use.2.kt

@@ -15,7 +15,7 @@ public  class Output(val d: Data) : Closeable {
     public fun doOutput(data: Int): Int = data
 }
 
-public open trait Closeable {
+public interface Closeable {
     open public fun close() {}
 }
 

js/js.translator/testData/inlineMultiFile/cases/with/with.2.kt

@@ -16,7 +16,7 @@ public  class Output(val d: Data) : Closeable {
     public fun doOutput(data: Int): Int = data
 }
 
-public open trait Closeable {
+public interface Closeable {
     open public fun close() {}
 }