[General] New Text Release

[Daniel Ingalls]

Folks -

I've just put out a new version of Text.js (with minor changes to  
Widgets.js, and CanvasExpt.js).  I've tested it quite a bit and feel  
it's ready to go out, but we should all be ready to revert if  
something is amiss.  I did *not* rewrite the kernel of text, which  
should be done some day.

The main things I did are...
Reused the structures (lines and "chunks") before and after the  
replacement when typing.  It's a lot better in big texts, but still a  
bit slow.  Some of the problem is clearly SVG thrashing around which  
can't be helped.  [Some day we should bundle characters when things  
get behind.  I opted not to do that this time, because the logic is  
almost all in event queuing]

Avoided one or two of the redundant composition passes for, eg, text  
in lists.

Fixed the bug that made it impossible to select in a line that was  
forced to wrap.

Pulled a few more classes in to the lively.Text namespace.

Fixed a bug with use of the UP key when cursor was on last line.

Made canvas LK only redraw the lines actually in the damage region.

Please test this, and let me know of any problems.  I will be  
traveling for the next couple of days, so if there are significant  
problems, we should revert until I can dig deep.  Also, let's test the  
ability to read old worlds (one of the big reasons I didn't redo the  
whole kernel) before we promote this code into the wiki.

Enjoy

	- Dan