Inconsistent naming of special-use attributes

[frank499]

special-use attributes for mailboxes ( \Archive, \Drafts, etc.) are handled differently by "cyradm setmd" and the autocreate function and xlist-options in imapd.conf. This was tested in cyrus-imap 3.8.4:

setmd INBOX.Archive /private/specialuse "\\archive"

and

setmd INBOX.Archive /private/specialuse "\\Archive"

will both create an attribute starting with an uppercase letter (\Archive).

The autocreate option xlist-Archive: Archive or xlist-archive: Archive will create an attribute with the first letter in lowercase (\archive). The same is true for other special use attributes.

Although attributes are not case-sensitive, naming should follow RFC6154 (first character is uppercase).