Fixed ismymbox() to look at Local-Mailbox as well as

Alternate-Mailboxes.  The problem was that when an alternate
mailbox was added to the list, the node for the local
mailbox information was lost.  Added check to test-mymbox.
Added test-repl, because this is where it was first noticed.
Also enhanced output with MHWDEBUG set to show the entire
list, not just each alternate mailbox as it is added to the
list.  [Bug #36635].