* mixi.el (mixi-make-release): New function.
(mixi-release-p): New macro.
(mixi-release-title): New function.
(mixi-release-time): Ditto.
(mixi-release-content): Ditto.
(mixi-release-list-page): New macro.
(mixi-release-list-regexp): New constant.
(mixi-get-releases): New function.
* mixi-utils.el (mixi-make-author): Support release object.
(mixi-make-id-1): Ditto.
(mixi-make-url): Ditto.
(mixi-make-reply-to): Ditto.
* sb-mixi.el (shimbun-mixi): Add release-cache.
(shimbun-mixi-default-group-alist): Add releases group.
(initialize-instance): Initialize release cache.
(shimbun-close): Clear release cache.
(shimbun-mixi-release-article): New function.
(shimbun-article): Use it.