Happy (if you could call it that!) to report AIX 7.1 works correctly :)

    RT sig 50 received with sival 0
    RT sig 50 received with sival 1
    RT sig 50 received with sival 2
    RT sig 51 received with sival 0
    RT sig 51 received with sival 1
    RT sig 51 received with sival 2
    RT sig 52 received with sival 0
    RT sig 52 received with sival 1
    RT sig 52 received with sival 2

Solaris 11 still appears backwards:

    RT sig 43 received with sival 0
    RT sig 43 received with sival 1
    RT sig 43 received with sival 2
    RT sig 42 received with sival 0
    RT sig 42 received with sival 1
    RT sig 42 received with sival 2
    RT sig 41 received with sival 0
    RT sig 41 received with sival 1
    RT sig 41 received with sival 2