Added a test to draw colored circles, making sure PPM output works.

Updated mandelbrot3 to fit in the default region size. This should work even with larger images, but region resizing is broken in kernels (#89, most likely).

Added kernel* to harlan-mode.
Added a color wheel test case. Also fixed a bug in the call graph generator that would include calls from kernels in functions.

There is still another bug where recursive calls are not always handled as they should.
Remove some unnecessary tracing.