Consider property external if all accessors are external #KT-13997 Fixed

compiler/testData/diagnostics/tests/ExternalAccessors.kt

@@ -0,0 +1,19 @@
+// See KT-13997
+
+class Foo {
+    var bar: Int // Ok
+        external get
+        external set
+}
+
+class Bar {
+    val foo: Int // Ok
+        external get
+
+    <!MUST_BE_INITIALIZED_OR_BE_ABSTRACT!>var baz: Int<!>
+        external get
+
+    <!MUST_BE_INITIALIZED_OR_BE_ABSTRACT!>var gav: Int<!>
+        external set
+}
+

compiler/testData/diagnostics/tests/ExternalAccessors.txt

@@ -0,0 +1,19 @@
+package
+
+public final class Bar {
+    public constructor Bar()
+    public final var baz: kotlin.Int
+    public final val foo: kotlin.Int
+    public final var gav: kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public final class Foo {
+    public constructor Foo()
+    public final var bar: kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}