Fix 0003635: status_resolved in email_api should be resolved.

M core/email_api.php

• Changed 'status_resolved' to 'resolved' before checking in preferences table (email_on_resolved).
• Changed 'status_closed' to 'closed' before checking in preferences table (email_on_closed).
• Check the existence of emailon???? field before using it. I had this in before, but it was removed in a recent commit.

git-svn-id: http://mantisbt.svn.sourceforge.net/svnroot/mantisbt/trunk@2437 <a class="text" href="/?p=mantisbt.git;a=object;h=f5dc347c">f5dc347c</a>-c33d-0410-90a0-b07cc1902cb9