Remove the meteor(4) driver.

Remove the meteor(4) driver.

It stopped building when -msoft-float was added to the options for building
the kernel.

FreeBSD removed it over 7 years ago, and so far I've heard of no one using
DragonFly because he had one of those old cards and we still had a driver,
so I guess it's safe to follow suit.

However, the <dev/video/meteor/ioctl_meteor.h> header is used by other,
working drivers (bktr(4) and cxm(4)) so we keep it. We also keep the
/usr/share/examples/meteor directory because the bktr(4) driver is based
on meteor(4) and bktr(4)'s manual page references these examples as being
mostly valid for bktr(4), too.