Cleanup poll/ppoll decoders

* poll.c (decode_poll): Split into print_pollfd, decode_poll_entering,
and decode_poll_exiting.
(sys_poll, sys_ppoll): Update callers.
* tests/ppoll.c: New file.
* tests/ppoll.expected: Likewise.
* tests/ppoll-v.expected: Likewise.
* tests/ppoll.test: New test.
* tests/Makefile.am (check_PROGRAMS): Add ppoll.
(TESTS): Add ppoll.test.
(EXTRA_DIST): Add ppoll.expected and ppoll-v.expected.
* tests/.gitignore: Add ppoll.
7 files changed