This header has been around since 2.6.23, however it's not being installed in /usr/include/linux but it exists in /usr/src/linux/include/linux...
ask on LKML / v4l-dvb-maintainer@linuxtv.org to see if it was supposed to be installed ...
The fix for this was finally pushed with 2.6.27. I'll just close out the issue because we can just require newer headers in the package moving forward.