Split the logic of

   static int setrootbyname(char *name);
out into
   dev_t getdiskbyname(char *name);

This makes it easy to create a new DDB command, which is the big reason
for the change.  You can now do the following in DDB:

Example rc.conf entry:
dumpdev="/dev/ad0s1b"   # Device name to crashdump to (if enabled).

db> show disk/ad0s1b
dev_t = 0xc0b7ea00
db> p *dumpdev
c0b7ea00

0 files changed, 0 insertions, 0 deletions