Got SDL2 update building, but it is completely untested beyond that.
Fixed some threading issues (did Go's threading model change?), and got Images and rect drawing working.
Got images and viewports working.
Moved util package contents to root starfish package.
Fixed text drawing.
Added a core event thread to backend.
Fixed more threading issues. The main thread now sets up the window and runs the main event loop.
Renamed backend package to plumbing.