Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

/* -> /*- for license, minor formatting changes

dheader and hheader were the same function, really, so rename one of
them to header, kill the other and use both with a different arg...

Use functions to make the program clearer.

Allow -d and -h as command line flags. These are used to generate
only the .h or _data.h files respectively. Restructure code to allow
for this.

Correct $FreeBSD$ style.

constify

Add usbdevs and friends.