Warnings from latest HEAD (zsh-5.9.0.3-test-357-g599af46) build

[Bart Schaefer <schaefer@xxxxxxxxxxxxxxxx>]

Apple clang version 17.0.0 (clang-1700.6.4.2)
Target: arm64-apple-darwin24.6.0
Thread model: posix

These are all from "54710: handle multibyte arguments in error messages"

gcc -c -I. -I../Src -I../Src -I../Src/Zle -I. -I/opt/local/include
-DHAVE_CONFIG_H -Wall -Wmissing-prototypes -ggdb  -o exec.o exec.c
exec.c:3303:8: warning: label followed by a declaration is a C23
extension [-Wc23-extensions]
 3303 |                             convchar_t opt = unmeta_one(cmdopt, NULL);
      |                             ^
1 warning generated.compctl.c:544:4: warning: label followed by a
declaration is a C23 extension [-Wc23-extensions]
  544 |                         convchar_t s = unmeta_one(p, NULL);
      |                         ^
1 warning generated.complete.c:800:3: warning: label followed by a
declaration is a C23 extension [-Wc23-extensions]
  800 |                 convchar_t c = unmeta_one(p, NULL);
      |                 ^
complete.c:1168:2: warning: label followed by a declaration is a C23
extension [-Wc23-extensions]
 1168 |         convchar_t c = unmeta_one(&argv[0][1], NULL);
      |         ^
2 warnings generated.

I'm surprised glob.c doesn't produce a similar error from

                default:
                    untokenize(--s);
-                   zerr("unknown file attribute: %c", *s);
+                   convchar_t attr = unmeta_one(s, NULL);
+                   zerr("unknown file attribute: %c", attr);
                    restore_globstate(saved);
                    return;

IIRC we've been trying to stick to the "declarations only at the start
of a block" convention.