#919: Use proper language variable. Thanks, Visman.
#922: Remove obsolete global variable. Thanks, Visman.
#902: Fix typos in language files. Thanks, Koos.
#902: Use more effective check for invalid value. Thanks, Koos.
#903: Various UTF-8 related fixes. Thanks, Koos.
#888: Fix undefined index errors. Thanks, Visman.
#904: Actually use old charset when converting to UTF-8. Thanks, Koos.
#921: Disable "Add forum" form when no categories exist
#911 Fix borders in Internet Explorer 11.0.1
Revert "#911 Fix borders in Internet Explorer 11.0.1"

This reverts commit df2d5ea29383fada95a9ccf8f72b2112dc920a87.
#911 Fix borders in IE11
Update version to 1.5.5.
#923: Use require_once to make sure function is not loaded twice.
Delete unreachable code.