make Rivet_i compatible with Rivet/YODA 3.1.2/1.8.3

Merged Christian Gutschow requested to merge cgutscho/athena:sync_rivet_with_21.6 into master

This change set syncs Rivet_i back with 21.6 and fix all the compiler issues previously seen. With this MR it should be fine to include it back into the Nightly builds.

FYI @zmarshal @ewelina @jchapman @lcorpe @dkar

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