NTP updates

Hi,

These patches clean up the NTP code a little and add the remaining user
space bits from the ntp nanokernel, so that it's e.g. now possible to
enable the nanosecond resolution, which should be useful to keep time in
a local network in sync (but it also needs an updated glibc/ntpd first).

I tried my best to also update the various user space APIs (e.g. compat,
vsyscall), but it would be great if someone could look over it, in case
I forgot something.

bye, Roman

--