Support routines for Token-Ring network drivers.

By Onno van der Linden.
Add TLINK_619_POLY.
Add if_token.h to INCS.
Add ARPHRD_IEEE802.
Add LLC_SNAPFRAMELEN.
Add support for Token-Ring source routes in the ARP cache.

By Onno van der Linden.
config(8) glue for Token-Ring and TROPIC drivers.
Recognise IBM and 3COM Token-Ring PnP cards and associate them with the tr
driver.
Regen.
Oops. RcsID police.
Appease GCC.
#ifdef FreeBSD some debug code as is done if if_fddisubr.c.
Add IBM and 3COM ISA Token-Ring drivers.
Make this understand Token-Ring.
From Onno van der Linden.
Add if_token.h.
Fix promiscuous modes - patches from Jason Wright.
VM_MBUF_SIZE is in terms of MCLBYTES, not CLBYTES.
Check for Sbus slave access errors.
Call bus_dma_load() with elevated priority.
Clarify NKMEMCLUSTERS and NMBCLUSTERS.
Call bus_dma_[un]load() at splbio.
Make the `...' actually appear in the case/esac syntax section.
Fix a space botch in the $@ example.
Kill warnings caused by the effective but wrong use of \[ and \] to
perform the function of \&[ and \&].