util_time fixes and improvements

[dob71]

This pull request contains 3 commits:

1. 40a8c03 asus: fix for clock jump on startup -> bugfix
2. 3b0690e util: use CLOCK_MONOTONIC_RAW for util_time if available -> use clock not affected by adjtime(x) adjustments if kernel supports it
3. 80a8254 util_timers: try all 16 clock IDs before timers test -> print out values returned by all clock supported by kernel before running the timers subsystem tests