x11: add a couple of tests

Add two tests:

    ./test/interactive-x11
which is like test/interactive-evdev, but should behave exactly like your
X keyboard and react to state and keymap changes - in other words, just
like typing in xterm. Press ESC to exit.

    ./test/x11
which currently should only print out the same keymap as
    xkbcomp $DISPLAY out.xkb
(modulo some whitespace and some constructs we do not support.)

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