Implemented isInitialized for lateinit properties + tests

backend.native/tests/build.gradle

@@ -1058,6 +1058,16 @@ task lateinit_localCapturedNotInitialized(type: RunKonanTest) {
     source = "codegen/lateinit/localCapturedNotInitialized.kt"
 }
 
+task lateinit_isInitialized(type: RunKonanTest) {
+    goldValue = "false\ntrue\n"
+    source = "codegen/lateinit/isInitialized.kt"
+}
+
+task lateinit_globalIsInitialized(type: RunKonanTest) {
+    goldValue = "false\ntrue\n"
+    source = "codegen/lateinit/globalIsInitialized.kt"
+}
+
 task kclass0(type: RunKonanTest) {
     source = "codegen/kclass/kclass0.kt"
 }

backend.native/tests/codegen/lateinit/globalIsInitialized.kt

@@ -0,0 +1,15 @@
+package codegen.lateinit.globalIsInitialized
+
+import kotlin.test.*
+
+lateinit var s: String
+
+fun foo() {
+    println(::s.isInitialized)
+}
+
+@Test fun runTest() {
+    foo()
+    s = "zzz"
+    foo()
+}

backend.native/tests/codegen/lateinit/isInitialized.kt

@@ -0,0 +1,18 @@
+package codegen.lateinit.isInitialized
+
+import kotlin.test.*
+
+class A {
+    lateinit var s: String
+
+    fun foo() {
+        println(::s.isInitialized)
+    }
+}
+
+@Test fun runTest() {
+    val a = A()
+    a.foo()
+    a.s = "zzz"
+    a.foo()
+}