updates: Avoid warning when on AC

When on AC, we wouldn't be resetting the timeout ID, and throwing
a warning later on, when the network state changed.
common: Fallback to GDK device type detection for Wacom touchscreens

libwacom support around touchscreens is unfortunately bumpy, and the
"TOUCH" value in the "Wacom Tool Type" property doesn't discern direct
from indirect touch devices, so ultimately rely on the GdkInputSource
to set the "system-integrated" flag expected on touchscreens.
common: Handle "cursor" tablet devices explicitly in GsdDeviceMapper

Just set the GSD_INPUT_IS_CURSOR flag on those, so the mapper is aware
if there are several of those around for mapping purposes.

https://bugzilla.gnome.org/show_bug.cgi?id=732111
wacom: Make cursor devices managed by GsdDeviceMapper

This allows for proper mapping and left/right handed modes on those too.

https://bugzilla.gnome.org/show_bug.cgi?id=732111