Adding options INSECURE to GENERIC

Hi all,

Apparently some sparc64 graphics drivers (radeonfb, ...) require
KAUTH_MACHDEP_UNMANAGEDMEM.

This used to mean "root", but now it means "root and insecure", so Xorg
doesn't work on a default configuration of netbsd/sparc64.

That means we have two options for good default configuration (Xorg "just
works")

1. Drop KAUTH_MACHDEP_UNMANAGEDMEM

After asking around, it looks like the code wrapped by the macro
PCI_MAGIC_IO_RANGE is not something that should be handed to userland if
securelevel is high.

2. Adding options INSECURE to GENERIC.

Thoughts on doing #2?