The `set_event` function requires that the transaction is already
inserted, or the event set is silently lost.
When parsing first IKEv2 message, first insert transaction, prepare
values, and borrow back inserted transaction to update it.
The mismatch between the types would randomly lead to the return code
of the Rust parser to be not correctly handled over the C/Rust
boundary. This would lead to the API considering a parser to be in
error state when it was not.
Add a new parser for Internet Key Exchange version (IKEv2), defined in
RFC 7296.
The IKEv2 parser itself is external. The embedded code includes the
parser state and associated variables, the state machine, and the
detection code.
The parser looks the first two messages of a connection, and analyzes
the client and server proposals to check the cryptographic parameters.