add "Auto-Submitted: auto-forwarded" to ignore mail test (#16190)

git-svn-id: http://svn.redmine.org/redmine/trunk@13205 e93f8b46-1217-0410-a6f0-8f06a7374b81
only ignore undesirable Auto-Submitted headers defined in RFC3834 (#16190)

Contributed by Felix Schäfer.

git-svn-id: http://svn.redmine.org/redmine/trunk@13206 e93f8b46-1217-0410-a6f0-8f06a7374b81
use \A instead of ^ for RegExp (#16190)

git-svn-id: http://svn.redmine.org/redmine/trunk@13207 e93f8b46-1217-0410-a6f0-8f06a7374b81