Since you have a DSO server type and your host (All-Inkl.com) allows you to use php_value and php_flag directives in an htaccess file then see this forum topic for where to add this code: http://forum.ait-pro.com/forums/topic/which-custom-code-text-box-do-i-use-to-add-custom-htaccess-code/#post-129
IMPORTANT NOTE: Very few server types allow these directives to be used in an htaccess file – 99% do not allow this code and 1% do allow this code. Typically these directives (without using php_value and php_flag in front of the directives) would be added in a custom php.ini file and not an htaccess file.