Various updates for userfaultfd man pages. To summarize the changes:

- Correctly / fully describe the two-step feature support handshake process.
- Describe new UFFDIO_POISON ioctl.
- Other small improvements (missing ioctls, error codes, etc).

Axel Rasmussen (10):
  userfaultfd.2: briefly mention two-step feature handshake process
  userfaultfd.2: reword to account for new fault resolution ioctls
  userfaultfd.2: comment on feature detection in the example program
  ioctl_userfaultfd.2: fix a few trivial mistakes
  ioctl_userfaultfd.2: describe two-step feature handshake
  ioctl_userfaultfd.2: describe missing UFFDIO_API feature flags
  ioctl_userfaultfd.2: correct and update UFFDIO_API ioctl error codes
  ioctl_userfaultfd.2: clarify the state of the uffdio_api structure on
    error
  ioctl_userfaultfd.2: fix / update UFFDIO_REGISTER error code list
  ioctl_userfaultfd.2: document new UFFDIO_POISON ioctl

 man2/ioctl_userfaultfd.2 | 254 ++++++++++++++++++++++++++++++++-------
 man2/userfaultfd.2       |  15 ++-
 2 files changed, 220 insertions(+), 49 deletions(-)

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2.42.0.459.ge4e396fd5e-goog