Kill the _GNU_SOURCE games

That was shortlived. There's no perfect way to do this, so retain the
note that it needs to be set for the application to use
io_uring_prep_ftruncate() or io_uring_register_iowq_aff(), and keep
the protection around those declarations in liburing.h.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
3 files changed