Spead2

- Undo the optimisation of using a single flow steering rule to cover multiple
multicast groups (see 11).

- Fix ``-c`` option to :program:`mcdump`.
- Fix a missing ``include`` that could be exposed by including headers in a
particular order.
- Make :cpp:class:`spead2::recv::heap`'s move constructor and move assignment
operator ``noexcept``.
- Add a `long_description` to the Python metadata.

- Update type stubs for new features in 1.11.0.

- Add :py:attr:`spead2.recv.Stream.allow_unsized_heaps` to support rejecting
packets without a heap length.
- Add extended custom memcpy support (C++ only) for scattering data from
packets.

- Use ibverbs multi-packet receive queues automatically when available
(supported by mlx5 driver).
- Automatically reduce buffer size for verbs receiver to match hardware limits
(fixed 64).
- Gracefully handle Ctrl-C in :program:`spead2_recv` and print statistics.
- Add typing stub files to assist checking with Mypy.
- Give a name to the argument of
:py:meth:`spead2.recv.Stream.add_inproc_reader`.
- Fix Python binding for one of the UDP reader overloads that takes an existing
socket. This was a deprecated overload.
- Add a unit test for ibverbs support. It's not run by default because it
needs specific hardware.

- Accelerate per-packet processing, particularly when `max_heaps` is large.
- Accelerate per-heap processing, particularly for heaps with few items.
- Add a fast path for single-packet heaps.
- Improve performance of the pcap reader by working on batches of packets.
- Provide access to ringbuffer size and capacity for diagnostics.
- Add extra fields to :py:class:`spead2.recv.StreamStats`.
- Add support for pcap files to the C++ version of :program:`spead2_recv`.
- Update the vendored pybind11 to 2.2.4 (fixes some warnings on Python 3.7).
- Deprecate netmap support in documentation.