Default options.debug_imap to 0 again, not False

This was overdone when switching from integers to booleans.
Here 0 and False are in fact probably equivalent, but it's still a bug.

archivemail

@@ -195,7 +195,7 @@ class Options:
     script_name          = os.path.basename(sys.argv[0])
     min_size             = None
     verbose              = False
-    debug_imap           = False
+    debug_imap           = 0
     warn_duplicates      = False
     copy_old_mail        = False
     archive_all          = False