Added a lot of comments, simplified call graphs.
Added full (not second-class) support for images coming from named sources (files, icon themes).
RrImage holds an RrImageSet. RrImageSet holds a bunch of RrImagePic, which are different sizes of a logical image.
RrImageSet objects can be merged if it is discovered they (will) share an RrImagePic. The RrImage objects are updated to use the new merged RrImageSet.
This changes how the imagecache works, you can load an image into it directly,
or you can load it by name (then it will load it from a file on disk).
NOTE: The name part is incomplete, as it needs to use the freedesktop.org icon
spec to search for the right file. Also to resize it should look for another
icon on disk with the same name but different size (icon themes).
Set version stuff to 3.5.0-rc1.
Copy the CHANGELOG from 3.4-working.
Rename the obt-4.0 and obrender-4.0 pkgconfig stuff to obt-3.5 and obrender-3.5
Rename the "render" directory to "obrender" so that the public headers can be
installed in <obrender/*>
