Fix for #84: Missing newline can lead to dropped lines.

Fix for #84: Missing newline can lead to dropped lines.

If the last zchar printed in a program is not ZC_RETURN, the Frotz core
exits without flushing the buffer, thereby leading to dropped lines.
This fix calls new_line() when the program finished, which emits a
ZC_RETURN to the output stream and flushes the buffer.