Regression in dtor/input.git/next - flush pending events on clock type change

[Benjamin Tissoires <benjamin.tissoires@redhat.com>]

Hi Anshul,

The commit 0c3e99437a66e4c869c60c2398449e6d98f3a988 in dtor/input.git/next
tree introduce an interesting regression in libinput. The tests fail :)

Actually, evemu-record and libinput switch the clock to monotonic when
opening an input node, and the first thing that gets queued is a
SYN_DROPPED event.

However, in the libinput test suite, events are the bare minimum, and
most of the tests contain only one event set (one EV_SYN).
When seeing the SYN_DROPPED, the clients are supposed to drain the events
until the next EV_SYN, and so they are losing the events that came long
after the ioctl call.
And in the end, the test suite does not receive any events.

Removing the evdev_queue_syn_dropped() call in the ioctl handling fixes
the test suite, and Peter suggested that maybe we should queue a
SYN_DROPPED event iff there are events in the queue.

Cheers,
Benjamin