Fixed|Client: Crash at shutdown

~WidgetActions accesses the singleton ClientApp's InputSystem, so
WidgetActions must be deleted first.
Fixed|Release: Compiler warning (unused argument)
Oculus Rift|libappfw: Updated for LibOVR 0.4.3

Version 0.4.3 has some API changes, so updated the use of LibOVR
accordingly. Still no luck with direct mode rendering, though.

Also some cleanup.