Updated shader names and code that uses them.
All of these shaders produce round points that are anti-aliased and blended against the background.
These were initially named SMOOTH because they replace glEnable(GL_POINT_SMOOTH). But SMOOTH in shader-land refers to vertex attribute interpolation (like glShadeModel(GL_SMOOTH)).
Using SMOOTH to mean two things is confusing, so we now use AA to mean "the point is anti-aliased".
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