JIS2004 support

JIS2004, which is a new Japanese national standard coded character set, adds three types of new characters:

1. Normal new characters that were not available before JIS2004 support.
2. Surrogate characters, which are two linked Unicode code points that represent a single character. The two Unicode code points are meaningless if they are separated.
3. Combining characters, which are two Unicode code points combined as one character. The two individual Unicode code points that combine to form a combining character can be displayed separately also.