Basic class members generation.

Split testData into 'classes' and 'expressions'.

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

@@ -0,0 +1,15 @@
+object FiveTimes
+
+class IntCell(var value: Int)
+
+interface IReceiver {
+    operator fun FiveTimes.iterator() = IntCell(5)
+    operator fun IntCell.hasNext() = value > 0
+    operator fun IntCell.next() = value--
+}
+
+fun IReceiver.test() {
+    for (i in FiveTimes) {
+        println(i)
+    }
+}