encoding: Fix encoding lookup with xmlOpenCharEncodingHandler Make xmlOpenCharEncodingHandler call xmlParseCharEncoding first so we prefer our own handlers for names like "UTF8". Only UTF-16 needs an exception. Make callers check the return value. For UTF-8, a NULL encoding doesn't mean an error. Remove unnecessary UTF-8 check from htmlFindOutputEncoder. Don't try to look up ASCII handler since the HTML handler is always available. Fix return code of xmlParseCharEncoding. Should fix #744.