keysym: fix xkb_keysym_is_upper/lower() to work properly

keysym: fix xkb_keysym_is_upper/lower() to work properly

Our current code (taken from the xserver) doesn't handle unicode keysyms
at all, and there seem to be some other changes compared to libX11,
which is what xkbcomp uses. So we just copy the code that does that from
libX11.
It would be much better to not have to hardcode unicode tables like
that, but it's probably better than dealing with glibc locale stuff for
now. It also doesn't affect our binary size much.

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