CharsetConverter: logicalToVisualBiDi refactoring
CharsetConverter: use FriBiDi's native UTF-32 charset to avoid double conversion
CharsetConverter: fix FriBiDi usage
CharsetConverter: cosmetics: move g_charsets[] closer to related functions
CharsetConverter: 'logicalToVisualBiDi' ability to fail on bad strings
CharsetConverter: consistency added: bidi can fail on bad sequence as well as conversion