task_messages_rewind(@optional remove_last_read)
Rewind the mailbox cursor of the current task so that the next call to
task_messages_next
and task_receive will access the oldest message in the mailbox.
Additionally if remove_last_read is true the message most
recently accessed by a call to task_messages_next will be removed from
the mailbox. When task_messages_next has not been called since the last call to task_receive or
task_messages_rewind, a call to task_messages_rewind with remove_last_read
set to true only resets the mailbox cursor (no message is removed).
Return void.