Value classes: Support 'value' modifier in parser

compiler/testData/psi/valueClass.kt

@@ -0,0 +1,35 @@
+class value Foo
+
+value private class Foo
+
+value @Bar class Foo
+
+value interface Foo
+
+value abstract class Foo
+
+value object Foo
+
+value fun foo(){}
+
+value class Foo
+
+value class Foo {
+    val l = 1
+    fun invoke()
+}
+
+private value class Foo
+
+expect value class Foo
+
+actual value class Foo
+
+@Bar value class Foo
+
+class TopLevel {
+    value class Foo
+}
+
+value
+class Foo