[AFS3-std] Standardization of GetCapabilties RPCs for AFS3 client and services

[Ken Hornstein]

>CAPABILITY FLAGS:
>
>Capability Flags will be registered with registrar@grand.central.org
>on a per-RPC basis.  The following capabilities are already in use:
>
>/* Viced Capability Flags */
>const VICED_CAPABILITY_ERRORTRANS       = 0x0001;
>const VICED_CAPABILITY_64BITFILES       = 0x0002;
>
>/* Cache Manager Capability Flags */
>const CLIENT_CAPABILITY_ERRORTRANS      = 0x0001;

I was thinking of a capability flag for RxTCP, but I'm wondering if it makes
sense to do that at the RPC level.  This presents a number of "interesting"
issues.  Specifically:

- Do we have the Rx library do this automatically?  This may not work, as
  that would mean the Rx library would have to make an "upper" level query
  (assuming we didn't have an Rx-level capability query).

- Do we have applications (or associated helper libraries) perform the query
  and then twiddle an Rx flag to tell it to use TCP?  This would make the
  Rx library simpler, at the cost of requiring applications to specifically
  request TCP usage.  This may be desirable; I'm not really sure.

--Ken