Add support for the Coda 6.x venus<->kernel interface. This extends

Add support for the Coda 6.x venus<->kernel interface. This extends
FIDs to be 128-bits wide and adds support for realms.

Add a new CODA_COMPAT_5 option, which requests support for the old
Coda 5.x interface instead of the new one.

Create a new coda5.ko module that supports the 5.x interface, and make
the existing coda.ko module use the new 6.x interface. These modules
cannot both be loaded at the same time.

Obtained from:	Jan Harkes & the coda-6.0.2 distribution,
		NetBSD (drochner) (CODA_COMPAT_5 option).