kernel32: Return LOCALE_INVARIANT from ConvertDefaultLocale.

dlls/kernel32/locale.c

@@ -2513,6 +2513,9 @@ LCID WINAPI ConvertDefaultLocale( LCID lcid )
 
     switch (lcid)
     {
+    case LOCALE_INVARIANT:
+        /* keep as-is */
+        break;
     case LOCALE_SYSTEM_DEFAULT:
         lcid = GetSystemDefaultLCID();
         break;

dlls/kernel32/tests/locale.c

@@ -3132,6 +3132,9 @@ static void test_ConvertDefaultLocale(void)
   LCID_RES(LOCALE_SYSTEM_DEFAULT, GetSystemDefaultLCID());
   LCID_RES(LOCALE_USER_DEFAULT,   GetUserDefaultLCID());
   LCID_RES(LOCALE_NEUTRAL,        GetUserDefaultLCID());
+  lcid = ConvertDefaultLocale(LOCALE_INVARIANT);
+  ok(lcid == LOCALE_INVARIANT || broken(lcid == 0x47f) /* win2k[3]/winxp */,
+     "Expected lcid = %08x, got %08x\n", LOCALE_INVARIANT, lcid);
 }
 
 static BOOL CALLBACK langgrp_procA(LGRPID lgrpid, LPSTR lpszNum, LPSTR lpszName,