Blender Git Loki

Long wanted feature; decent ESC processing in composite nodes.

Works simple; just check for

if(node->exec & NODE_BREAK)
break;

The main process (node processor) sets such a flag, checking for esc
20 times per second. That means you can check for ESC while doing image
processing without much cpu overhead.

Currently only added in blur nodes and defocus. Needs to be added all over,
nice for others... needs careful tests too.

What we now could do is even calling ESC on editing commands or mouseclicks
in composite editor? Could give user feeling of interactive app :) Further,
finished nodes are kept in memory anyway.