Consider sharing time using a shared page

[OlliV]

This is an old idea that I have written down a several times before.

A vdso-like page could contain at least:

• nanotime
• realtime

Since 4kB is a lot of space it could be a good idea to share some code or something else too.

Linux does this: https://www.man7.org/linux/man-pages/man7/vdso.7.html