When processing events from the EQ, _always_ call the processInputProc of the
matching device. For XI devices, this proc is wrapped in three layers.
Core event handling is wrapped by XI event handling, which is wrapped by XKB.
A core event now passes through XKB -> XI -> DIX.
This gets rid of a sync'd grab problem: with the previous code, core events
did disappear during a sync'd device grab on account of mieqProcessInputEvents
calling the processInputProc of the VCP/VCK instead of the actual device. This
lead to the event being processed as normal instead of being enqueued for
later replaying.
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