Expose interop enum .value through CEnum interface

Interop/Runtime/src/main/kotlin/kotlinx/cinterop/Types.kt

@@ -214,6 +214,9 @@ sealed class CPrimitiveVar : CVariable {
     open class Type(size: Int) : CVariable.Type(size.toLong(), align = size)
 }
 
+interface CEnum {
+    val value: Number
+}
 abstract class CEnumVar : CPrimitiveVar()
 
 // generics below are used for typedef support

Interop/StubGenerator/src/main/kotlin/org/jetbrains/kotlin/native/interop/gen/jvm/StubGenerator.kt

@@ -612,7 +612,7 @@ class StubGenerator(
 
         val baseTypeMirror = mirror(e.baseType)
 
-        block("enum class ${e.kotlinName.asSimpleName()}(val value: ${e.baseType.kotlinType})") {
+        block("enum class ${e.kotlinName.asSimpleName()}(override val value: ${e.baseType.kotlinType}) : CEnum") {
             e.constants.forEach {
                 out("${it.name.asSimpleName()}(${it.value}),")
             }