libs/libc/locale/langinfo: implement the nl_langinfo function

1. the nl_langinfo can help to pass the
ltp/open_posix_testsuite/strftime testcases
2. the implementation are referred to https://pubs.opengroup.org/onlinepubs/9699919799/functions/nl_langinfo.html

Signed-off-by: guoshichao <guoshichao@xiaomi.com>

libs/libc/locale/lib_langinfo.c

@@ -24,6 +24,7 @@
 
 #include <nuttx/config.h>
 
+#include <stdlib.h>
 #include <langinfo.h>
 
 #ifdef CONFIG_LIBC_LOCALE
@@ -42,6 +43,134 @@
 
 FAR char *nl_langinfo(nl_item item)
 {
+  switch (item)
+    {
+      case CODESET:
+
+        /* if current locale encode length are 1, the codeset are ASCII,
+         * then we support utf-8
+         */
+
+        if (MB_CUR_MAX == 1)
+          {
+            return "ASCII";
+          }
+
+        return "UTF-8";
+      case RADIXCHAR:
+        return ".";
+      case THOUSEP:
+        return ",";
+      case ABDAY_1:
+        return "Sun";
+      case ABDAY_2:
+        return "Mon";
+      case ABDAY_3:
+        return "Tue";
+      case ABDAY_4:
+        return "Wed";
+      case ABDAY_5:
+        return "Thu";
+      case ABDAY_6:
+        return "Fri";
+      case ABDAY_7:
+        return "Sat";
+      case DAY_1:
+        return "Sunday";
+      case DAY_2:
+        return "Monday";
+      case DAY_3:
+        return "Tuesday";
+      case DAY_4:
+        return "Wednesday";
+      case DAY_5:
+        return "Thursday";
+      case DAY_6:
+        return "Friday";
+      case DAY_7:
+        return "Saturday";
+      case ABMON_1:
+        return "Jan";
+      case ABMON_2:
+        return "Feb";
+      case ABMON_3:
+        return "Mar";
+      case ABMON_4:
+        return "Apr";
+      case ABMON_5:
+        return "May";
+      case ABMON_6:
+        return "Jun";
+      case ABMON_7:
+        return "Jul";
+      case ABMON_8:
+        return "Aug";
+      case ABMON_9:
+        return "Sep";
+      case ABMON_10:
+        return "Oct";
+      case ABMON_11:
+        return "Nov";
+      case ABMON_12:
+        return "Dev";
+      case MON_1:
+        return "January";
+      case MON_2:
+        return "Feburary";
+      case MON_3:
+        return "March";
+      case MON_4:
+        return "April";
+      case MON_5:
+        return "May";
+      case MON_6:
+        return "June";
+      case MON_7:
+        return "July";
+      case MON_8:
+        return "August";
+      case MON_9:
+        return "September";
+      case MON_10:
+        return "October";
+      case MON_11:
+        return "November";
+      case MON_12:
+        return "December";
+      case AM_STR:
+        return "AM";
+      case PM_STR:
+        return "PM";
+      case D_T_FMT:
+        return "%a %b %e %H:%M:%S %Y";
+      case D_FMT:
+        return "%F";
+      case T_FMT:
+        return "%T";
+      case T_FMT_AMPM:
+        return "%I:%M:%S %p";
+      case ERA:
+        return "";
+      case ERA_D_FMT:
+        return "";
+      case ALT_DIGITS:
+        return "";
+      case ERA_D_T_FMT:
+        return "";
+      case ERA_T_FMT:
+        return "";
+      case CRNCYSTR:
+        return "";
+      case YESEXPR:
+        return "^[yY]";
+      case NOEXPR:
+        return "^[nN]";
+      case YESSTR:
+        return "yes";
+      case NOSTR:
+        return "no";
+    }
+
   return "";
 }