keysym: Do not convert UTF-32 to deprecated keysyms Before this commit, some code points could be converted to deprecated keysym. This is incorrect, because the relevant keysyms are all deprecated because their mapping to Unicode is uncertain! Ensure that `xkb_utf32_to_keysym()` never returns deprecated keysyms, because there is either another non-deprecated keysym or in last resort we always have the correct keysym available in the Unicode keysym range.