fix send mail with safe mode (phpmailer patch)

ref 1.   http://www.xugj.org/modules/QandA/index.php?topic_id=2200
ref 2-1. http://core.trac.wordpress.org/ticket/20970
ref 2-2. http://core.trac.wordpress.org/attachment/ticket/20970/20970.patch

[ja]セーフモード環境下でメール送信が行なわれない問題の修正です。[/ja]