When using a `print` statement to write to a file that has raw output
enabled, NUL characters in string are no longer interpreted into "\0",
no newline is appended afterwards, and each argument to `print` is
written to the file without any additional separation.
(Re)Assigning to identifiers with the &raw_output attribute should also
now correctly apply the attribute to the file value being assigned.
Note that the write_file BiF should already be capable of raw string
data to a file, expect it bypasses the print_hook event.
Addresses #474
