libcanberra avoid gtk3 dragged in at gtk2 environments

* build two versions of canberra-gtk-play for gtk2 and gtk3.
* move canberra-gtk-play to libcanberra-gtk2 and canberra-gtk3-play to
  libcanberra-gtk2.

Signed-off-by: Andreas Müller <schnitzeltony@googlemail.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>