VAX kernel work again.

[Matt Thomas <matt%3am-software.com@localhost>]

Note that the new rnd support exposed a gcc bug so to run -current since
the rnd changes went in, you will need to rebuild your toolchain.

From simh:

2670116+184280 [212688+204119]=0x31ee44
Copyright (c) 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005,
    2006, 2007, 2008, 2009, 2010, 2011, 2012
    The NetBSD Foundation, Inc.  All rights reserved.
Copyright (c) 1982, 1986, 1989, 1991, 1993
    The Regents of the University of California.  All rights reserved.

NetBSD 5.99.63 (GENERIC)
MicroVAX 3800/3900
total memory = 65468 KB
avail memory = 59672 KB
mainbus0 (root)
cpu0 at mainbus0: KA655, CVAX microcode rev 6 Firmware rev 83
lance at mainbus0 not configured
uba0 at mainbus0: Q22
dz1 at uba0 csr 160100 vec 304 ipl 17
mtc0 at uba0 csr 174500 vec 774 ipl 17
mscpbus0 at mtc0: version 5 model 3
mscpbus0: DMA burst size set to 4
mscpbus0: couldn't attach drive (no free items)
uda0 at uba0 csr 172150 vec 770 ipl 17
mscpbus1 at uda0: version 3 model 3
mscpbus1: DMA burst size set to 4
mscpbus1: couldn't attach drive (no free items)
qe0 at uba0 csr 174440 vec 764 ipl 17: delqa, hardware address 08:00:2b:aa:bb:cc
rlc0 at uba0 csr 174400 vec 160 ipl 17
rl0 at rlc0 drive 0: RL01, drive not loaded
rl1 at rlc0 drive 1: RL01, drive not loaded
rl2 at rlc0 drive 2: RL01, drive not loaded
rl3 at rlc0 drive 3: RL01, drive not loaded
ts0 at uba0 csr 172520 vec 224 ipl 17: TS11
ts0: rev 0, extended features enabled, transport offline
mt0 at mscpbus0 drive 0: TK50
mt1 at mscpbus0 drive 1: TK50
mt2 at mscpbus0 drive 2: TK50
mt3 at mscpbus0 drive 3: TK50
ra0 at mscpbus1 drive 0: RA92
ra1 at mscpbus1 drive 1: RA82
ra2 at mscpbus1 drive 2: RA82
ra3 at mscpbus1 drive 3: RRD40
ra0: size 2940951 sectors
ra1label: 0
: no disk label: size 3908000 sectors
ra2: size 3908000 sectors
ra3label: 0
: no disk label: size 1331200 sectors
boot device: ra0
root on ra0a dumps on ra0b
root file system type: ffs