Basic class members generation.

Split testData into 'classes' and 'expressions'.

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

@@ -0,0 +1,15 @@
+class Ref(var value: Int)
+
+interface IHost {
+    fun String.extLength() = length
+}
+
+fun test1(x: String?) = x?.length
+fun test2(x: String?) = x?.hashCode()
+fun test3(x: String?, y: Any?) = x?.equals(y)
+
+fun test4(x: Ref?) {
+    x?.value = 0
+}
+
+fun IHost.test5(s: String?) = s?.extLength()