Expose the default context at the python level too.
Disable fill() and clip() since they are untested.
Introduce refcounts for buffers and kernels.  The major change with this is that views don't have to be careful not to free their gpudata pointer anymore, which should reduce bugs.  Also there is no need to maintain the "parent" object alive anymore, which is another source of bugs.

All told I hope I never see a segmentation fault due to mismanagement of the gpudata pointers again.
Enable more warnings when building.
Fix IndentationError.
Fix the testsuite to not check "OWNDATA".  All tests pass.