Add warning for initializers with obsolete syntax

Expected 'init' keyword before class initializer

idea/testData/checker/AnonymousInitializers.kt

@@ -1,18 +1,18 @@
 trait NoC {
-  <error>{
+  <error>init {
 
   }</error>
 
   val a : Int get() = 1
 
-  <error>{
+  <error>init {
 
   }</error>
 }
 
 class WithC() {
   val x : Int
-  {
+  init {
     $x = 1
     <error>$y</error> = 2
     val <warning>b</warning> = x
@@ -21,7 +21,7 @@ class WithC() {
 
   val a : Int get() = 1
 
-  {
+  init {
     val <warning>z</warning> = <error>b</error>
     val <warning>zz</warning> = x
     val <warning>zzz</warning> = <error>$a</error>

idea/testData/checker/Objects.kt

@@ -18,7 +18,7 @@ package toplevelObjectDeclarations
   val x = A.foo()
 
   val y = object : Foo(x) {
-    {
+    init {
       x + 12
     }
 

idea/testData/checker/Properties.kt

@@ -16,7 +16,7 @@ class Test() {
     var a : Int = 111
     var b : Int get() = $a; set(x) {a = x; $a = x}
 
-   {
+   init {
     <error>$b</error> = $a
     $a = <error>$b</error>
     a = <error>$b</error>

idea/testData/checker/infos/PropertiesWithBackingFields.kt

@@ -46,7 +46,7 @@ class TestPCParameters(w : Int, <warning>x</warning> : Int, val <info>y</info> :
 
   val <info>xx</info> = w
 
-  {
+  <info>init</info> {
     w + 1
   }
 

idea/testData/checker/regression/ScopeForSecondaryConstructors.kt

@@ -1,5 +1,5 @@
   class Foo(var bar : Int, var barr : Int, var barrr : Int) {
-    {
+    init {
       bar = 1
       barr = 1
       barrr = 1
@@ -7,7 +7,7 @@
       this : Foo
     }
 
-    {
+    init {
       bar = 1
       this.bar
       1 : Int