Extract extend codepoints out in seperate array (#713)

IsCombining() is a hotpath when rendering the screen.
Most of the time is spent doing bisearch on the word break interval list
to check it characters has the extend property.

Create a seperate table for intervals with the extend property,
so they can just be searched in isCombining().

Also some of the intervals in the word break interval list
were consecutive and could be combined to reduce the
size of the list.

This gives a ~25% performance improvement when running the benchmark