DragonFlyBSD

After importing the vendor's man page for libmagic, I noticed that there's
a cross-reference to errno(3) instead of errno(2). Since I'm still trying
to figure out this patch system we have instead of using vendor branches,
I'd like some input on the following patch to fix libmagic.3 which is also
available at http://leaf.dragonflybsd.org/~pavalos/libmagic.diff.

--Peter