Shorten a status text description.

Instead of just copying-and-pasting from 802.11, edit the description a
bit; this squelches a Coverity warning (it thought we might have
forgotten a comma in the list), and also means we don't quite print out
as much.

(If Table 8-37 "Status codes" in 802.11-2012 had names for *all* the
status codes, we could use the names instead of the explanatory text,
but, for some unknown reason, it doesn't.)
Get rid of fetch whose result isn't used.

Put in a comment to indicate what we're processing (and that we fetch
the entire array as a 32-bit number and extract the nibbles from it).
Squelch a Coverity warning.

If you pass in a value of oidlen and oidsize such that we can't store
*anything* into OID, this would be a problem; that *shouldn't* ever
happen, but this makes the code a bit more obviously correct.
Clean up the first-item handling a bit.

This makes it look a bit more like the handling of other items.