Add the option of making kernel-mode tests.

Fixes #130, at least the ability.  Will need to figure out which tests to
add.
Correct screenshots of 16-bit framebuffers.
Update triangle test with expected image.
Fix cache problem in gpu/complex test.
Fix timing problem in gpu/commands/material test.
Correct expected result of gpu/rendertarget test.
Add some extra size tests for block transfers.
Merge pull request #155 from unknownbrackets/gpu-tests

Clean up and fix some GPU tests