Fair point. Do you have an alternative in mind? I can think of three:
1. Use printf instead. It's supposed to be much lighter weight.
2. Require a flag during build to create a "debug" version that include this error
logging
3. Both 1 and 2 above.

Thoughts?

I've thought a bit more about this and I think what we should do here is add a logging
helper to CLD2, and use that. We can then twiddle the logger on/off based on a DEFINE,
just like many other logging frameworks. I don't want to add a third-party logging
solution because the overhead just isn't worth it for our very sparse usage, at least
not at present.

We can switch to printf for now, and go down the define flag avenue later if it seems
worthwhile. Sound good?

Checked in compact_lang_det_impl.cc and found the standard pattern used here, which
is fprintf([stderr|stdout], ...). So that's the way to go.

Committed as r164.