Kotlin: Add a test

This caused a stack overflow on a branch, due to the recursino between
the class and the extension function.

java/ql/test/kotlin/library-tests/extensions_recursion/element.expected

@@ -0,0 +1,27 @@
+| file://:0:0:0:0 |  |
+| test.kt:0:0:0:0 | TestKt |
+| test.kt:0:0:0:0 | test |
+| test.kt:2:1:4:1 | bar |
+| test.kt:2:6:2:6 | T |
+| test.kt:2:9:2:14 | <this> |
+| test.kt:2:31:4:1 | { ... } |
+| test.kt:3:5:3:15 | return ... |
+| test.kt:3:12:3:15 | true |
+| test.kt:6:1:10:1 | <Expr>; |
+| test.kt:6:1:10:1 | <obinit> |
+| test.kt:6:1:10:1 | <obinit>(...) |
+| test.kt:6:1:10:1 | Foo |
+| test.kt:6:1:10:1 | Foo |
+| test.kt:6:1:10:1 | equals |
+| test.kt:6:1:10:1 | hashCode |
+| test.kt:6:1:10:1 | other |
+| test.kt:6:1:10:1 | super(...) |
+| test.kt:6:1:10:1 | toString |
+| test.kt:6:1:10:1 | { ... } |
+| test.kt:6:1:10:1 | { ... } |
+| test.kt:6:11:6:11 | T |
+| test.kt:7:5:9:5 | foo |
+| test.kt:7:24:9:5 | { ... } |
+| test.kt:8:9:8:20 | return ... |
+| test.kt:8:16:8:20 | bar(...) |
+| test.kt:8:16:8:20 | this |

java/ql/test/kotlin/library-tests/extensions_recursion/element.ql

@@ -0,0 +1,5 @@
+import java
+
+from Element e
+where e.fromSource()
+select e

java/ql/test/kotlin/library-tests/extensions_recursion/test.kt

@@ -0,0 +1,11 @@
+
+fun <T> Foo<T>.bar(): Boolean {
+    return true
+}
+
+class Foo<T> {
+    fun foo(): Boolean {
+        return bar()
+    }
+}
+