l4/sys/syscalls.h: No such file or directory

Hi,

I'm using the following example provided by Michael Hohmuth in 2000 to
create new tasks and threads:
http://os.inf.tu-dresden.de/pipermail/l4-hackers/2000/000384.html

I've placed the code in a copy of the hello example, but added
> REQUIRES_LIBS   = l4sys
to the Makefile.
The directory structure is located at './l4/pkg/taskcreat'.

Nevertheless, compilation is terminated due to a fatal error:
> ./l4/pkg/taskcreat/server/src/main.c:5:29: fatal error:
l4/sys/syscalls.h: No such file or directory

Why is syscalls.h missing here?

Best regards,
Valentin