xzdec: Use setlocale() via tuklib_gettext_setlocale()

xzdec isn't translated and didn't have locale-specific behavior
in the past. On Windows with UTF-8 in the application manifest,
setting the locale makes a difference though:

  - Without any setlocale() call, non-ASCII filenames don't display
    properly in Command Prompt unless one first uses "chcp 65001"
    to set the console code page to UTF-8.

  - setlocale(LC_ALL, "") is enough to make non-ASCII filenames
    print correctly in Command Prompt without using "chcp 65001",
    assuming that the non-UTF-8 code page (like 850) supports
    those non-ASCII characters.

  - setlocale(LC_ALL, ".UTF8") is even better because then mbrtowc() and
    such functions use an UTF-8 locale instead of a legacy code page.
    The tuklib_gettext_setlocale() macro takes care of this (without
    enabling any translations).

Fixes: 46ee006162

src/xzdec/xzdec.c

@@ -41,6 +41,7 @@
 #endif
 
 #include "getopt.h"
+#include "tuklib_gettext.h"
 #include "tuklib_progname.h"
 #include "tuklib_exit.h"
 
@@ -419,6 +420,17 @@ main(int argc, char **argv)
 	(void)prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
 #endif
 
+	// We need to set the locale even though we don't have any
+	// translated messages:
+	//
+	//   - This is needed on Windows to make non-ASCII filenames display
+	//     properly when the active code page has been set to UTF-8
+	//     in the application manifest. Use the helper macro from
+	//     tuklib_gettext.h instead of plain setlocale(LC_ALL, "")
+	//     because on Windows the standard call isn't enough for
+	//     full UTF-8 support.
+	tuklib_gettext_setlocale();
+
 	// Parse the command line options.
 	parse_options(argc, argv);