Rasterizer Optimizations

This PR includes several optimizations to the rasterizer, each found to give a small boost in performance on my test case. (First 25 frames of 3dscraft, note that this isn't GPU-bound ATM, so not the best representative of a performance increase.) Each commit message has the run time for the test as well as the delta from the previous commit on its commit message.
Was just curious if you added it for any particular reason. Is there even any difference in the code a compiler is likely to compile from the previous version?