(coding-system-change-eol-conversion): New function.

(prefer-coding-system): Don't call `update-coding-systems-internal';
use function `coding-category-list' instead of variable
`coding-category-list'; use `set-coding-priority-list' instead of
`set-coding-priority'; modify `eol-type' for XEmacs.
(language-info-alist): Delete description about
`nonascii-translation'; delete `nonascii-translation' feature; don't
set up `charset-origin-alist'; don't set up
`default-sendmail-coding-system'.