Some recent changes

[Charlie Brej]

I made some changes today, nothing major and most stuff I discussed on IRC 
already but just to keep everyone up to speed.
(Ray could you just cast your eye over them)

Migrate from image to pixel-buffer

- Images now use a pixel-buffer to keep their data. This avoids some duplication.
- There were a couple image transformation functions, I moved their body to 
pixel-buffer. Don't use these in new code as I will remove them once I migrate 
the plugins over.
- If you want to perform transformations then use the pixel-buffer. There is a 
new function to convert an image to a pixel buffer to help you.

Scripted plugin uses pixel-buffer

- Migrated the scripted plugin to use pixel-buffers to store the image data.
- Implemented the text to image function now that it is trivial with 
pixel-buffers. This has exact same behaviour as the one that mandriva has as a 
patch.
- Example of the text rendering shown with the message callback.