msvcrt: _towupper_l only uppercase a-z in C locale.

dlls/msvcrt/tests/string.c

@@ -3642,7 +3642,6 @@ static void test_C_locale(void)
             ok(ret == exp, "expected %x, got %x for C locale\n", exp, ret);
         }
         else
-        todo_wine_if(ret != i)
             ok(ret == i, "expected self %x, got %x for C locale\n", i, ret);
     }
 
@@ -3672,7 +3671,6 @@ static void test_C_locale(void)
                 ok(ret == exp, "expected %x, got %x for C locale\n", exp, ret);
             }
             else
-            todo_wine_if(ret != j)
                 ok(ret == j, "expected self %x, got %x for C locale\n", j, ret);
         }
 

dlls/msvcrt/wcs.c

@@ -2478,6 +2478,19 @@ MSVCRT_size_t CDECL MSVCRT_wcsnlen(const MSVCRT_wchar_t *s, MSVCRT_size_t maxlen
  */
 int CDECL MSVCRT__towupper_l(MSVCRT_wint_t c, MSVCRT__locale_t locale)
 {
+    MSVCRT_pthreadlocinfo locinfo;
+
+    if(!locale)
+        locinfo = get_locinfo();
+    else
+        locinfo = locale->locinfo;
+
+    if(!locinfo->lc_handle[MSVCRT_LC_CTYPE]) {
+        if(c >= 'a' && c <= 'z')
+            return c + 'A' - 'a';
+        return c;
+    }
+
     return toupperW(c);
 }