See the branch:
This partially solves Bug #27178.
I could use a -priv.h or -private.h suffix for the headers if you want, but I prefer -internal.h (as seen in telepathy-glib), since these things are really library-scoped, which doesn't correspond to C++ private at all (but does correspond almost exactly to G_GNUC_INTERNAL).
Most of the build infrasctucture was inherited from Empathy, that's why it differs a lot from TP.
I'd enable also:
-# declaration-after-statement \
unless you have specific reason to let it off.
For the rest, OK!
Ignore comment#2 which was for for another branch of yours, I remove the review+ for the moment.
It look good and it compiles against the current Empathy trunk.
Empathy though depends on TPL on a strict version basis, so it wouldn't break anything, it is just to know that it works.
I rebased a current big branch of mine on top of internalize and it seems working properly as well without big manual works.
You can merge it.