Basic class members generation.

Split testData into 'classes' and 'expressions'.

compiler/testData/ir/irText/expressions/when.kt

@@ -0,0 +1,27 @@
+object A
+
+fun testWithSubject(x: Any?) =
+        when (x) {
+            null -> "null"
+            A -> "A"
+            is String -> "String"
+            in setOf<Nothing>() -> "nothingness?"
+            else -> "something"
+        }
+
+fun test(x: Any?) =
+        when {
+            x == null -> "null"
+            x == A -> "A"
+            x is String -> "String"
+            x in setOf<Nothing>() -> "nothingness?"
+            else -> "something"
+        }
+
+fun testComma(x: Int) =
+        when (x) {
+            1, 2, 3, 4 -> "1234"
+            5, 6, 7 -> "567"
+            8, 9 -> "89"
+            else -> "?"
+        }