delayed delete

[Wesley Craig]

I've updated this bug report:

	https://bugzilla.andrew.cmu.edu/show_bug.cgi?id=2871

to include a patch adding support for a configuration option,  
delete_mode, which takes the options "delayed" and "immediate".  The  
patch saves certain kinds of deleted mail in the cyrus spool  
hierarchy.  Patch has been tested out of production, tho we're  
expecting to deploy it in production at UMich soon.  Comments welcome.

:wes