Move blackBoxFile() testData to box/ directory

Delete all test methods (and empty test classes), since they'll be
auto-generated

compiler/testData/codegen/box/classes/kt1018.kt

@@ -0,0 +1,12 @@
+public class StockMarketTableModel() {
+
+    public fun getColumnCount() : Int {
+        return COLUMN_TITLES?.size!!
+    }
+
+    class object {
+        private val COLUMN_TITLES : Array<Int?> = arrayOfNulls<Int>(10)
+    }
+}
+
+fun box() : String = if(StockMarketTableModel().getColumnCount()==10) "OK" else "fail"