locale.c: Omit an extra copy

In this case in Perl_setlocale(), we can just return the plain result
from setlocale(), as, if something further needs to be done that would
destroy it, that is taken care of already at the time.

On per-thread locale platforms, the result already is in a per-category
buffer.

locale.c

@@ -2671,8 +2671,8 @@ Perl_setlocale(const int category, const char * locale)
     }
 
     /* Here, an actual change is being requested.  Do it */
-    retval = save_to_buffer(setlocale_i(cat_index, locale),
-                            &PL_setlocale_buf, &PL_setlocale_bufsize);
+    retval = setlocale_i(cat_index, locale);
+
     if (! retval) {
         DEBUG_L(PerlIO_printf(Perl_debug_log,
                               "Perl_setlocale returning (null)\n"));