Squashed commit of the following:

Squashed commit of the following:

commit 1c610279b21ac778ab96fd2fb01fa0bbc8f363ce
Author: Mike Brady <4265913+mikebrady@users.noreply.github.com>
Date:   Mon Sep 12 15:07:15 2022 +0100

    * Bump NQPTP_SHM_STRUCTURES_VERSION to 8.
    * Remove the ability to handle multiple instances of AirPlay-2-capable Shairport Sync on the same system -- it seems clear that clients can not use this facility.
    * Greatly simplify NQPTP by only monitoring PTP information coming from the client, ignoring all other PTP information.
    * Improve the accuracy of the clock by taking correction field information into account.
    * In addition to trying to restart a clock that is silent, also send a restart to a clock if the clock's grandmaster appears to have stopped.

    Squashed commit of the following:
        Add some experimental exploratory code.
        Ignore the INSTALL document. Let INSTALL always be autogenerated.
        Enhanced and corrected ptp definitions.
        Fix shm name to work with FreeBSD. Update the SHM version.
        Change order of includes to avoid a compilation error in FreeBSD
        Fix potential bugs in finding a clock ID in a FreeBSD device.
        Only try to restart a stopped clock if it's the clock itself that has stopped and not a different grandmaster. Allow fast changes for up to one second after the start of mastership.
        Make the code to restart a clock a separate function and call it if a clock gets stuck. Include the correction field in the calculation of the precise origin timestamp. If a new clock is out by more than -4 seconds, treat it as a discontinuity rather than noise.
        Add a net-to-host converter for 64-bit arithmetic