lib/locale.t: Use I18N::Langinfo, not POSIX::localeconv()

Now that Langinfo is ported to every box, it requires less work than
localeconv(), and offers more choices.  This commit changes to use it,
and for more info when debugging, gets some additional info from it.

lib/locale.t

@@ -54,6 +54,7 @@ BEGIN {
 }
 
 use feature 'fc';
+use I18N::Langinfo qw(langinfo CODESET CRNCYSTR RADIXCHAR);
 
 # =1 adds debugging output; =2 increases the verbosity somewhat
 our $debug = $ENV{PERL_DEBUG_FULL_TEST} // 0;
@@ -1052,9 +1053,11 @@ foreach my $Locale (@Locale) {
 
     my $is_utf8_locale = is_locale_utf8($Locale);
 
+    debug "code set = " . langinfo(CODESET);
     debug "is utf8 locale? = $is_utf8_locale\n";
 
-    debug "radix = " . disp_str(localeconv()->{decimal_point}) . "\n";
+    debug "radix = " . disp_str(langinfo(RADIXCHAR));
+    debug "currency = " . disp_str(langinfo(CRNCYSTR));
 
     if (! $is_utf8_locale) {
         use locale;
@@ -2429,7 +2432,7 @@ foreach my $Locale (@Locale) {
         $test_names{$locales_test_number} = 'Verify atof with locale radix and negative exponent';
         $problematical_tests{$locales_test_number} = 1;
 
-        my $radix = POSIX::localeconv()->{decimal_point};
+        my $radix = langinfo(RADIXCHAR);
         my @nums = (
              "3.14e+9",  "3${radix}14e+9",  "3.14e-9",  "3${radix}14e-9",
             "-3.14e+9", "-3${radix}14e+9", "-3.14e-9", "-3${radix}14e-9",