Fix behaviour to match RFC 6265 on encountering domain mismatch.
Make wget abort if --post-file does not exist

Signed-off-by: Darshit Shah <darnir@gmail.com>
Add test to ensure correct return code on --post-file failure

Signed-off-by: Darshit Shah <darnir@gmail.com>
warc: correctly write the field length in the skip length field