Pull up revisions:
src/distrib/utils/sysinst/defs.h revision 1.163
src/distrib/utils/sysinst/disks.c revisions 1.125,1.126
src/distrib/utils/sysinst/main.c revisions 1.65,1.66
src/distrib/utils/sysinst/arch/emips/md.h revision 1.4
src/distrib/utils/sysinst/arch/i386/md.h revision 1.69
src/distrib/utils/sysinst/arch/vax/md.h revision 1.21
(requested by abs in ticket #386).

- Replace the CD_NAME definition with a CD_NAMES comma separate list,
the default remains "cd0a", but i386 sets "cd0a", "mcd0a" while vax
takes "cd0a", "racd0a"
- Add get_default_cdrom() to disks.c, which is called in init(). This
checks the contents of hw.disknames against CD_NAMES. The first one
found (minus partition letter) is picked, otherwise the first entry
in CD_NAMES is used
The primary beneficiary is vax systems with an MSCP but no SCSI CD
drive, which now default to (a valid) racd0a rather than an invalid
cd0a. The obvious example being simh-vax

Trying to print a function pointer as a string is likely to cause tears.
While here, don't match on the unit either

Do not assign to a const pointer, but set the value of the target variable
instead. Makes sysinst at least start up again.