fastcgi and older versions of tcpdf don't work together

This isn't an actionable bug, but more of a note for the next person who runs into it. In general, fastcgi with php-fpm has been working well with CiviCRM, but the version of the eternal TCPDF library included in 4.2 and before outputs multiple Content-Type headers, giving a fatal error in the apache log looking like:

error parsing headers: duplicate header 'Content-Type'

The easy solution is just to remove the duplicate header output rows from the tcpdf code, or you could probably replace the whole library with an updated one.