package/multimedia: mark festival packages as broken

After spending a couple of hours on it today, I'm still unable to get
speech-tools to build and install properly with a uClibc toolchain.

So I'm giving up. Mark the entire thing broken as the text-to-speech
stuff is unlikely to be used very much on the kind of small systems
we're targetting.

Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>