Fix compilation after ceylon/ceylon-sdk@bfbda4a

`ceylon.file.Writer` now has a `writeBytes({Byte*} bytes)` method that we need to supply.

Can @gavinking or perhaps @davidfestal please test if this works? I’m getting another error – something “refers to the missing type `Image` – but that might be due to a messed up local setup.

See ceylon/ceylon-sdk@bfbda4af9232feabca14faadf40b8b8d07e96e57, ceylon/ceylon.formatter@17c825014b31b797d1c2df21924d4605a64dcf11.