API DeleteInboxItem

__NOTOC__
Requests the server to remove a mailbox message.
 DeleteInboxItem(index)
==Arguments==
:;index: - the index of the message (1 is the first message)
==Details==
* DeleteInboxItem() returns immediately but one must listen for .
* The asynchronous request may fail for different reasons, such as an invalid index or when another deletion request is already in progress
* DeleteInboxItem() is an unconditional request; the server does not check whether the message still has an item or money attached.
** The confirmation box that appears in game for these conditions is instead triggered by before calling DeleteInboxItem.
** Note that InboxItemCanDelete is not a permission-checking function, it is just an API for determining whether a message is returnable (and thus has a misleading name). All messages are in fact deletable.