Add a macro that wraps wl_display_roundtrip() and check for errors. It
is a macro, so that the assert would show the relevant file and line
number.
This will also catch protocol errors, that would go unnoticed otherwise.
All roundtrips in tests are replaced with the check.
Signed-off-by: Pekka Paalanen <ppaalanen@gmail.com>
Remaining use case was when we move the pointer. This doesn't change
geometry so we can just use a wl_display_roundtrip() to make sure
we get the request to the server and receive the resulting events.
A round trip is sufficient here. We need to make sure that the server
has received the wl_test request and that we've received the event
that the request triggers. The wl_display_roundtrip() helper does
exactly that: it sends a wl_display.sync request, which will hit the
server after the wl_test requests and thus the wl_callback.done event
will come back after the server has seen all the previous requests and
after we've handled all preceeding event.
