When was dot notation for dotted property paths added?

[Urs Liska]

Somewhere in 2.17. David introduced the change from

\override Stem #'length
to
\override Stem.length

I would like to know in which LilyPond version this appeared.
Somehow I don't seem to be able to think of the right search terms to 
locate the commit(s).

Concretely, I have a snippet that needs \version "2.17.10" and I would 
like to know which notation I can use.

TIA
Urs