Even though \u has been supported since C++11, the latest i686-w64-mingw32-windres on Cygwin doesn't support it, which corrupted any non-ASCII character in the screen saver's dialog boxes.
To work around the problem that originally made me switch from \x to \u, mklocale.pl now splits the string literal wherever a new \x escape sequence "absorb" subsequent characters that happened to be hexadecimal digits. This results in uglier header files, but the real source code is the .txt files.