Change that darn dratted auto-purge folders when you delete 'em thing with

Change that darn dratted auto-purge folders when you delete 'em thing with
Courier. Sometimes it works with Courier, but it seems that more often than
not, Courier complains if you try to delete a folder and send it to Trash
(seems like we don't close or unselect the folder after copying the contents
to Trash but before we try to delete it).

In any case, since subfolders of trash Will technically work, my safety
don't shoot yourself comments aren't really appropriate.

Also flipped the question on it's head, so it will hopefully make more sense
(value stored is the same, just turned the question upside-down).

git-svn-id: https://svn.code.sf.net/p/squirrelmail/code/trunk/squirrelmail@5329 7612ce4b-ef26-0410-bec9-ea0150e637f0