struct member cn_nameptr 'const', since they should never be used to
modify the path name. (Only the pathname buffer, cn_pnbuf, should be
modified.) Propagate the const poisoning to code that uses the namei
and componentname structs.
Implement cd9660_blkatoff() and use it.
Reduce lots of multiplies and divides to shifts.
Make some macros look more like UFS.
Make isodirino() return the inumber rather than poke it into the abyss.
