Blender Git Loki

Depsgraph: Change to how id tagging happens

Basically the idea is:

- Builder re-sets the LIB_DOIT flag, so it's guaranteed no left over
flags happened (it's not guaranteed LIB_DOIT is reset everywhere).

- Functions checks this flag directly, without using wrapping the check
with functions which kinda hides actual logic (that wouldn't be a
problem if this flag was only used by depsgraph).

- Removed flag check/set wrapping functions. Found them being rather
obscure and not really necessary from the beginning.