[BUGFIX] Use setReplyTo and setCc instead of add*

The methods addReplyTo and addCc accept strings as parameters, but we
need the setReplyTo and setCc which accept arrays. This will make the
reply-to and recipient-copy options work in formMail.

Change-Id: Ia3826d51f53ffe497f4c3b25957f0332fb89e81e
Resolves: #25301
Releases: 4.6
Reviewed-on: http://review.typo3.org/1442
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn