[imp] Turning off 'Purge Deleted' when use_trash is a Bad Thing

[Christopher Audley]

I've been testing RELENG_3, which will presumably be RC3, and come 
across one problem that will really confuse users.  When the option to 
move deleted messages to the trash folder is set to true, the 'Hide 
Deleted' and 'Purge Deleted' commands are no longer presented to the user.

This assumes that no messages marked deleted will be in folders other 
than 'Trash'.  This may be true when IMP is the only MUA that users are 
using, but it is generally false.  Netscape 6.x, for instance, follows 
the move to Trash paradigm but only occationally does a folder 
compaction which is responsible for removing files marked for deletion. 
 Outlook Express default to just marking messages for deletion.

The result is that users will often see files marked for deletion in 
their mailboxes that they can neither hide nor purge when using IMP.

Please undo this change.

Thanks
Chris