Add override tests

java/ql/test/kotlin/query-tests/MissingOverrideAnnotation/MissingOverrideAnnotation.expected

@@ -0,0 +1,3 @@
+| Test.kt:16:14:18:5 | m | This method overrides $@; it is advisable to add an Override annotation. | Test.kt:2:10:4:5 | m | A.m |
+| Test.kt:22:14:22:24 | o | This method overrides $@; it is advisable to add an Override annotation. | Test.kt:12:5:12:11 | o | I.o |
+| Test.kt:24:14:24:22 | getP | This method overrides $@; it is advisable to add an Override annotation. | Test.kt:8:10:8:18 | getP | A.getP |

java/ql/test/kotlin/query-tests/MissingOverrideAnnotation/MissingOverrideAnnotation.qlref

@@ -0,0 +1 @@
+Advisory/Declarations/MissingOverrideAnnotation.ql

java/ql/test/kotlin/query-tests/MissingOverrideAnnotation/Test.kt

@@ -0,0 +1,25 @@
+open class A {
+    open fun m(): Int {
+        return 23
+    }
+
+    private fun n() {}
+
+    open val p = 5
+}
+
+interface I {
+    fun o()
+}
+
+class B : A(), I {
+    override fun m(): Int {
+        return 42
+    }
+
+    fun n() {}
+
+    override fun o() { }
+
+    override val p = 7
+}