Fixed issue #14098: When sending mail, use TYPO3_CONF_VAR for default from...

Fixed issue #14098: When sending mail, use TYPO3_CONF_VAR for default from address if no other address is provided, credits Jeff Segars and Marcus Krause

git-svn-id: https://svn.typo3.org/TYPO3v4/Core/trunk@10167 709f56b5-9817-0410-a4d7-c38de5d9e867