Evas textblock: Implement format invalidation points support.
Evas textblock: Implement format invalidation points support.

This lets us only relayout what's needed also when inserting formats.
This means inserting <b> </> for example is now as fast as inserting any
other char and doesn't cause a complete relayout.

git-svn-id: 24a995eca3b83137dd7eab3408044d7832e202f7@58958 7cbeb6ba-43b4-40fd-8cce-4c39aea84d33

antognolli/Evas,antognolli/Evas,antognolli/Evas,antognolli/Evas