Non-US-ASCII From: names can cause email validation error

http://forum.civicrm.org/?topic=8400 - it seems a From: name Fred Troussé get properly encoded to =?utf-8?Q?"Fred=20Trouss=C3=A9"=20?=, but then hits a validation error either in the CiviCRM codebase or at the SMTP error. We should fix this by properly quoting the From: name.