color-lcms: print transformation id instead of pointer

Pointer values are hard to track for humans, being long numbers. Now
that we have unique id for each color transformation, print that instead
of the pointer. It is a small number easy to track for humans.

Transformation id numbers do get re-used aggressively, so you have to
keep track of what is being destroyed and created over time when reading
logs. Pointers had the same caveat, just a lot more random.

The prefix 't' indicates "transformation".

Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.com>