Make stdlib map freezing aware. (#1876)

backend.native/tests/build.gradle

@@ -707,6 +707,11 @@ task freeze4(type: RunKonanTest) {
     source = "runtime/workers/freeze4.kt"
 }
 
+task freeze5(type: RunKonanTest) {
+    goldValue = "OK\n"
+    source = "runtime/workers/freeze5.kt"
+}
+
 task atomic0(type: RunKonanTest) {
     disabled = (project.testTarget == 'wasm32') // Workers need pthreads.
     goldValue = "35\n" + "20\n" + "OK\n"

backend.native/tests/runtime/workers/freeze5.kt

@@ -0,0 +1,42 @@
+package runtime.workers.freeze5
+
+import kotlin.test.*
+object Keys {
+    internal val myMap: Map<String, List<String>> = mapOf(
+            "val1" to listOf("a1", "a2", "a3"),
+            "val2" to listOf("b1", "b2")
+    )
+
+    fun getKey(name: String): String {
+        for (key in myMap.keys) {
+            if (key == name) {
+                return key
+            }
+        }
+        return ""
+    }
+
+    fun getValue(name: String): String {
+        for (value in myMap.values) {
+            if (value.contains(name)) {
+                return name
+            }
+        }
+        return ""
+    }
+
+    fun getEntry(name: String): String {
+        for (entry in myMap.entries) {
+            if (entry.key == name) {
+                return entry.key
+            }
+        }
+        return ""
+    }
+}
+@Test fun runTest() {
+    assertEquals("val2", Keys.getKey("val2"))
+    assertEquals("a1", Keys.getValue("a1"))
+    assertEquals("val1", Keys.getEntry("val1"))
+    println("OK")
+}