Install runtime headers for mirage-xen.

- Provides C code with headers that match the minimal libc
  and OCaml functions they will be linked against.
Merge branch 'minios-gntmap' of git://github.com/djs55/mirage-platform
Sync CHANGES
Fix "infinite" delay when no timeouts are scheduled

Was passing an interval as a time.
Merge pull request #104 from talex5/fix-clock

Fix "infinite" delay when no timeouts are scheduled
Depend on mirage-profie to add tracing support