Get bsd-user host page protection code working on FreeBSD hosts

Use kinfo_getvmmap(3) on FeeBSD >= 7.x and /compat/linux/proc on older
FreeBSD.  (kinfo_getvmmap is preferred since /compat/linux/proc is
usually only mounted on hosts also using the Linuxolator.)

This patch is a bit hacky because the includes needed for kinfo_getvmmap
conflict with other definitions in exec.c by default so I had to `trick
around' a little, but I built the result in FreeBSD 6.4-stable and
7.2-stable tbs and on 8-stable on the host so the hacks at least
should be stable.  (If this is a problem maybe we could also move the
kinfo_getvmmap invocations into a seperate source file but that would
be more work...)

Signed-off-by: Juergen Lock <nox@jelal.kn-bremen.de>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
