Add a test for the results of key sequences

Add a test for the results of key sequences

This test verifies the core purpose of this library, which is to
translate the user's keypresses into keysyms according to the keymap and
the XKB specification.

The tests emulate a series of key presses, and checks that the resulting
keysyms are what we expect.

Several of the tests currently fail, and plenty more should be added and
maybe split up.

It also currently uses an RMLVO keymap, which comes from the
xkeyboard-config data set, and whose behaviour may change in the future.
So it should probably be changed to use several files of our own, but
it's OK for now.

Signed-off-by: Ran Benita <ran234@gmail.com>