fix debug msg
fix pre-init

set the internal relative time - don't rely on hwtimer_now() being
called externally
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addresses https://github.com/RIOT-OS/RIOT/pull/501#discussion_r8881054
update internal timer on hwtimer_arch_set
reduce HWTIMERMINOFFSET
Merge pull request #501 from LudwigOrtmann/native_hwtimer_fixup

Native hwtimer fixup