updated for version 7.3.177

Problem:    MS-Windows: mkdir() doesn't work properly when 'encoding' is
            "utf-8".
Solution:   Convert to utf-16. (Yukihiro Nakadaira)

src/os_win32.c

@@ -2639,6 +2639,30 @@ mch_isdir(char_u *name)
     return (f & FILE_ATTRIBUTE_DIRECTORY) != 0;
 }
 
+/*
+ * Create directory "name".
+ * Return 0 on success, -1 on error.
+ */
+    int
+mch_mkdir(char_u *name)
+{
+#ifdef FEAT_MBYTE
+    if (enc_codepage >= 0 && (int)GetACP() != enc_codepage)
+    {
+	WCHAR	*p;
+	int	retval;
+
+	p = enc_to_utf16(name, NULL);
+	if (p == NULL)
+	    return -1;
+	retval = _wmkdir(p);
+	vim_free(p);
+	return retval;
+    }
+#endif
+    return _mkdir(name);
+}
+
 /*
  * Return TRUE if file "fname" has more than one link.
  */