tmtests/tm27: Fixes for RTEMS_DEBUG
score: Add and use _Thread_Update_cpu_time_used()

Fix _times().
score: ISR lock API changes
score: Rename tod.h to todimpl.h
score: Delete _TOD_Activate and _TOD_Deactivate
score: Add and use _TOD_Is_set()
score: Move nanoseconds since last tick support

Move the nanoseconds since last tick support from the Watchdog to the
TOD handler.  Now the TOD managment is encapsulated in the TOD_Control
structure.
score: Use an ISR lock for TOD

Two issues are addressed.

1. On single processor configurations the set/get of the now/uptime
timestamps is now consistently protected by ISR disable/enable
sequences.  Previously nested interrupts could observe partially written
values since 64-bit writes are not atomic on 32-bit architectures in
general.  This could lead to non-monotonic uptime timestamps.

2. The TOD now/uptime maintanence is now independent of the giant lock.
This is the first step to remove the giant lock in _Thread_Dispatch().