xfree86: Fix event data alignment in inputtest driver

This fixes address sanitizer errors when running unit tests. The
additional copying may reduce performance by a small amount, but we
don't care about that because this driver is used for testing only.

Signed-off-by: Povilas Kanapickas <povilas@radix.lt>
4 jobs for inputtest-data-alignment in 3 minutes and 8 seconds (queued for 2 seconds)