input: Synchronize multiple mice handled through evdevmouse plugin

input: Synchronize multiple mice handled through evdevmouse plugin

EvdevMouseManager now receives relative pointer coordinates from each
connected mouse and is then responsible for clamping and forwarding them
to the QWindowSystemInterface. This avoids jumping cursors when multiple
pointer devices are connected. This does not change behavior together
with devices handled through the evdevtouch plugin.

Change-Id: I7feb358f68c3b3ebd138116224b4747c88c6761f
Reviewed-by: Girish Ramakrishnan <girish.1.ramakrishnan@nokia.com>