tmf.core: fix timestamp normalization clamping

tmf.core: fix timestamp normalization clamping

This patch fixes a behavior issue with timestamps. Offsetting and
normalizing timestamps no longer overflows, nor does it throw
arithmetic exceptions.

This is done by using a saturated add and mult method from TmfTimestamp.
The saturated math should have a negligeable impact on performance.

Change-Id: I8f6fc7fc930586897923bb8510574ec4c4c668b3
Signed-off-by: Matthew Khouzam <matthew.khouzam@ericsson.com>
Reviewed-on: https://git.eclipse.org/r/67501
Reviewed-by: Patrick Tasse <patrick.tasse@gmail.com>
Tested-by: Patrick Tasse <patrick.tasse@gmail.com>
Reviewed-by: Hudson CI