Fix xkbparse.y compilation

Fix xkbparse.y compilation

Thanks to autotools happily building stale generated sources, I hadn't
actually ever built my xkbparse.y changes.  Fix that so it not only
compiles, but works.  This seems to parse long keycodes correctly,
although I very much would not recommend testing this by declaring
0x1fffffff as your highest keycode.

Signed-off-by: Daniel Stone <daniel@fooishbar.org>