(mel-encoding-module-alist): New variable.

(mel-encoding-module-alist): New variable.
(mel-use-module): New function.
(mel-find-function): New function.
(mel-define-service): New macro.
(mime-encode-region): Use `mel-find-function'; abolish variable
`mime-encoding-method-alist'.
(mime-decode-region): Use `mel-find-function'; abolish variable
`mime-decoding-method-alist'.
(mime-decode-string): Use `mel-find-function'; abolish variable
`mime-string-decoding-method-alist'.
(encoded-text-encode-string): New function.
(encoded-text-decode-string): New function.
(base64-encoded-length): New function (moved from mel-b.el and
mel-dl.el).
(Q-encoding-printable-char-p): New function (moved from mel-q.el, and
renamed from `q-encoding-printable-char-p').
(Q-encoded-text-length): New function (moved from mel-q.el, and
renamed from `q-encoding-encoded-length').
(mime-insert-encoded-file): Use `mel-find-function'; abolish variable
`mime-file-encoding-method-alist'.
(mime-write-decoded-region): Use `mel-find-function'; abolish variable
`mime-file-decoding-method-alist'.