Fix open_basedir issues when accessing styles- and language-management

After a new installation of phpbb 3.0.7 PL1, you can not open styles in the ACP.

Get the following error message:
[phpBB Debug] PHP Notice: in file /includes/acp/acp_styles.php on line 646: is_dir() [function.is-dir]: open_basedir restriction in effect. File(./../styles/..) is not within the allowed path(s): (/:/usr/share/php/:/tmp/)
[phpBB Debug] PHP Notice: in file /adm/index.php on line 150: Cannot modify header information - headers already sent by (output started at /includes/functions.php:3493)
[phpBB Debug] PHP Notice: in file /adm/index.php on line 152: Cannot modify header information - headers already sent by (output started at /includes/functions.php:3493)
[phpBB Debug] PHP Notice: in file /adm/index.php on line 153: Cannot modify header information - headers already sent by (output started at /includes/functions.php:3493)
[phpBB Debug] PHP Notice: in file /adm/index.php on line 154: Cannot modify header information - headers already sent by (output started at /includes/functions.php:3493)

/includes/acp/acp_styles.php the line 646:
if (!is_dir($phpbb_root_path . 'styles/' . $file))

and Please see also in the includes/acp/acp_language.php line 1123:
if (!is_dir($phpbb_root_path . 'language/' . $file))

Also already in the German phpbb written https://www.phpbb.de/community/viewtopic.php?f=73&t=203883&start=10#p1167399

Thanks
wintstar