RFAPI code needs changes for 64-bit time_t

[eqvinox]

With 64bit time_t (cf. #15881), it is no longer possible to store a timestamp (64bit) in a pointer (32bit).

The RFAPI code does this:

https://github.com/FRRouting/frr/blob/65c3b1e4c888610d72c761ec3a7d2b1cfb84bfa0/bgpd/rfapi/rfapi_rib.c#L1797

This needs to be fixed. Considering the "relative quiet" (all recent changes seem to be fixes to go along with refactors elsewhere, or the occasional memleak fix) in RFAPI, someone from LabN probably needs to step up to do this…