This is a fix for issue 0002819 (Valid email address rejected...)

• core/email_api.php* core/email_api.php
  (email_get_rfc822_regex): new function to produce a regex for validating emails closer to RFC 822 specs

  (email_is_valid): cleanup a bit, mostly to use email_get_rfc822_regex()

git-svn-id: http://mantisbt.svn.sourceforge.net/svnroot/mantisbt/trunk@1705 <a class="text" href="/?p=mantisbt.git;a=object;h=f5dc347c">f5dc347c</a>-c33d-0410-90a0-b07cc1902cb9