libipt, insn: distinguish between enabled and resumed

With CPL filtering, tracing is regularly disabled and re-enabled.

Most of the time, tracing continues from where it stopped last time.  Sometimes,
however, it may continue from a different position.  We would like to
distinguish those two cases.

Add a new pt_insn flag 'resumed' to indicate that tracing continued from where
it stopped at the preceding disable.  The existing flag 'enabled' now indicates
that we cannot tell that for sure.  Either we know that tracing continued from a
different position, or we can't tell.

Change-Id: Id4dd5d79dfd1927146e298c4c3ff44c143d5ac50
Signed-off-by: Markus Metzger <markus.t.metzger@intel.com>