"In our country, everything is possible", as the Russians say.
The problem is that the language file and the config file are read in the same loop (in lines 197-198 of the snippet code). For the language to become part of the $files array that lists files to include, the config file would need to have been read in prior to this.
A quick fix: you can create your own language parameter in your config file, let us call it $c_language, and test for its existence after the file-inclusion loop. If it exists, you can use it to include the relevant language file. This then sets $_lang, which is the deciding factor in all the language settings that follow.
Insert the following after the foreach loop in lines 194-206 of the snippet code (
foreach ($files as $filename => $filevalue) { ... } ) and before line 208 (
//---Initiate Class---------)
if (isset($c_language)) {
include $ditto_base."lang/$c_language.inc.php";
}
In your config file, set $c_language as required, e.g. :
Obviously this could do with a little bullet-proofing, but it worked for me testing with ’german’ and ’francais’ as values and seeing what [+next+] and [+previous+] produced with pagination set.

KP