If there are other mice, they should show up in the device list, and
we want to report events from those devices instead of the core events.
However, if XInput isn't supported or we can't find other mice in the
device list, we'll add the core pointer and interpret normal mouse events.

--HG--
extra : convert_revision : svn%3Ac70aab31-4412-0410-b14c-859654838e24/trunk%403454