This is too strict, and causes symbols/cz to fail parsing. Instead, just
emit a warning (not shown by default):
xkbcommon: WARNING: cz:75:19: unknown escape sequence in string literal
https://bugs.freedesktop.org/show_bug.cgi?id=68056
Reported-By: Gatis Paeglis <gatis.paeglis@digia.com>
Signed-off-by: Ran Benita <ran234@gmail.com>