Unused parameter warnings

[Marc Nieper-Wißkirchen]

When compiling Gnulib with -Wunused-parameter, I get the following
report from GCC:

lib/localename.c: In function 'gl_locale_name_thread_unsafe':
lib/localename.c:3117:57: error: unused parameter 'categoryname'
[-Werror=unused-parameter]
 3117 | gl_locale_name_thread_unsafe (int category, const char *categoryname)
      |                                             ~~~~~~~~~~~~^~~~~~~~~~~~
lib/localename.c: In function 'gl_locale_name_posix':
lib/localename.c:3256:49: error: unused parameter 'categoryname'
[-Werror=unused-parameter]
 3256 | gl_locale_name_posix (int category, const char *categoryname)
      |                                     ~~~~~~~~~~~~^~~~~~~~~~~~
lib/localename.c: In function 'gl_locale_name_environ':
lib/localename.c:3321:29: error: unused parameter 'category'
[-Werror=unused-parameter]
 3321 | gl_locale_name_environ (int category, const char *categoryname)
      |                         ~~~~^~~~~~~~

Wouldn't it make sense to insert MAYBE_UNUSED from "attribute.h" here?

Thanks,

Marc