eventfd2: fix flags decoding

* configure.ac (AC_CHECK_HEADERS): Add sys/eventfd.h.
* eventfd.c: Include <fcntl.h>.
[HAVE_SYS_EVENTFD_H] Include <sys/eventfd.h>.
Include "xlat/efd_flags.h".
(do_eventfd): Use efd_flags for flags decoding.
* xlat/efd_flags.in: New file.
* tests/eventfd.c: New file.
* tests/eventfd.expected: Likewise.
* tests/eventfd.test: New test.
* tests/Makefile.am (check_PROGRAMS): Add eventfd.
(TESTS): Add eventfd.test.
(EXTRA_DIST): Add eventfd.expected.
* tests/.gitignore: Add eventfd.
8 files changed