Evas textblock: split the visual layouting to two stages:

Evas textblock: split the visual layouting to two stages:
1. Split to logical layout units.
2. Order the logical layout units in a visual way.
This lets us cache the results of the first part (unless the text changes), which makes everything a lot faster in the OT case, and quite faster in the regular case.
There are still some issues unresolved in this commit that will be resolved in future commits:
1. No support for async rendering - yes, I forgot I'm supposed to support that.
2. native_size should probably be calculated in another way because the current one is slow and if we already have the logical items it should be a piece of cake...

SVN revision: 56504