Add ofp_requestforward_reason

This will be used when encoding and decoding masks for
set async and get async reply properties.

Signed-off-by: Simon Horman <horms@verge.net.au>
Add ofp_async_config_prop_{reasons,experimenter}

This will be used when encoding and decoding
set async and get async reply properties.

Signed-off-by: Simon Horman <horms@verge.net.au>
Update get async reply and set async for protocol v5

The current implementation of get async reply and set async for protocol v5
is follows that of protocol v4. However, the OpenFlow 1.4.0 specification
defines a rather different format. This patch updates the implementation to
follow the specification.

Signed-off-by: Simon Horman <horms@verge.net.au>
Merge branch 'v5-async' into v5+v4-ext