file extensions for Openoffice

[Francesco Potorti`]

In the following places:

lisp/dos-w32.el:51:    ("\\.\\(arc\\|zip\\|pak\\|lzh\\|zoo\\)$" . t)
lisp/files.el:1434:     ("\\.\\(arc\\|zip\\|lzh\\|zoo\\|jar\\)\\'" . 
archive-mode)
lisp/gnus/gnus-uu.el:74:    
("\\.\\(tar\\|arj\\|zip\\|zoo\\|arc\\|gz\\|Z\\|lzh\\|ar\\|lha\\)$"
lisp/international/mule.el:1286:  
'(("\\.\\(arc\\|zip\\|lzh\\|zoo\\|jar\\|tar\\|tgz\\)\\'" . no-conversion)

the extension .sxi should be added.  It indicates a slide presentation
in Openoffice format, which is the same as a jar format, as far as I can
see.  If anyone knows other Openoffice extensions, they could be added
as well.