Your headers seem broken. What should happen (i.e. in upstream kernel git) is:
let's have a look on my headers (debian sid kernel 2.6.30 s2-liplianin dvb)
Did you look in /usr/include/linux/dvb/... or in /usr/src/linux/... ?
/usr/src/s2-liplianin/linux
For compiling userspace stuff (which vdr for sure is), the versions in /usr/include are used.
not so necessary
it's possible to change this behaviour
--> edit --> Make.config --> DVBDIR = /usr/src/s2-liplianin/linux
Goga