Add basic support for Rar.
(archive-find-type): Recognize Rar's signature. (archive-desummarize): New fun. (archive-summarize): Use it to restore the buffer's data in case someone wants to switch to some other major mode. (archive-resummarize): Use it as well. (archive-rar-summarize, archive-rar-extract): New functions.
Showing with 128 additions and 31 deletions