* lisp/gnus.el (gnus-version-number): Update to 6.10.4.
* lisp/gnus-sum.el (gnus-nov-parse-line): Use `nnheader-nov-field',
`nnheader-nov-read-integer' and `nnheader-nov-read-message-id' instead of
`gnus-nov-field', `gnus-nov-read-integer' or
`nnheader-generate-fake-message-id'; use `eobp' instead of
`(= (following-char) ?\n)' for checking whether a misc field exists or not.
(gnus-nov-field): Abolished.
(gnus-nov-skip-field): Abolished.
(gnus-nov-read-integer): Abolished.
* lisp/nnheader.el (nnheader-parse-nov): Use `nnheader-nov-read-message-id'
instead of `nnheader-nov-field' or `nnheader-generate-fake-message-id'.
(nnheader-nov-read-message-id): New macro.
(nnheader-nov-read-integer): New implementation.
(nnheader-nov-field): New implementation.
(nnheader-nov-next-field): New macro.