Nice goodie: Preview renders!
- Added new preview.blend, allowing super wide cinemascope previews
- Draws nicely blended inside widget type, rounded corners
- Preview now renders using all available cpus/cores.
- Uses - hopefully rock stable - method, which doesn't copy or
allocate anything for previews, but just uses render API calls.
- Multiple previews are possible! But, added provision in Jobs
manager to only render one preview job at a time. If you start
more preview jobs, they're suspended until it's their turn.
Bugfix: new buttons context code crashed when going full-window.
Tweaks are still needed for notifiers. I have to figure out still
how to retrieve SpaceButs button view types...
- Previewrender code back, commented out a lot of bad cruft,
nothing works or is linked even!
- Added NC_GROUP notifier type, used in editgroup.c and
listened to in 3dview and outliner
