52f1b88749
These were not thread safe, and could not be: to be useful, a thread looking up a time conversion could cache the result, but it would be using the global (shared) copy of the map (because lookup is read-only, and so no write-copy is required). But inserting into the lookup table wasn't lock protected (and shouldn't be because otherwise that defeats the point of RCU). So just drop it.
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