Kotlin: Add while statements

java/ql/test/kotlin/library-tests/stmts/stmts.expected

@@ -1,4 +1,5 @@
-| stmts.kt:2:41:8:1 | { ... } |
+| stmts.kt:2:41:10:1 | { ... } |
 | stmts.kt:3:8:3:12 | if (...) |
 | stmts.kt:4:15:4:19 | if (...) |
-| stmts.kt:7:5:7:16 | return ... |
+| stmts.kt:7:5:8:16 | while (...) |
+| stmts.kt:9:5:9:16 | return ... |

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

@@ -4,6 +4,8 @@ fun topLevelMethod(x: Int, y: Int): Int {
     } else if(x < y) {
     } else {
     }
+    while(x > y)
+        return x
     return x + y
 }