Fix JS source maps for initialization of variables captured by class

js/js.translator/testData/lineNumbers/innerClass.kt

@@ -0,0 +1,9 @@
+class A(val x: Int) {
+    inner class B {
+        fun foo() {
+            println(x)
+        }
+    }
+}
+
+// LINES: 1 2 4