tests/ppoll.c: use libtests
tests/ppoll.c: use libtests

* tests/ppoll.c (main): Use assert, perror_msg_and_skip,
and perror_msg_and_fail.

cuviper/strace,cuviper/strace,Saruta/strace,Saruta/strace,Saruta/strace,Saruta/strace,Saruta/strace,cuviper/strace,cuviper/strace,cuviper/strace