StimulusDisplay now relies on GL_ARB_framebuffer_object (instead of GL_EXT_framebuffer_object and GL_EXT_framebuffer_blit)
Removed option to disable redrawing stimulus display on every refresh, as all GPUs supported by OS X 10.8 support the required OpenGL extension
Cosmetic tweak in StimulusDisplay
StimulusDisplay now renders each frame only once, on an offscreen framebuffer, and then blits that single framebuffer to the main and mirror displays as needed
StimulusDisplay now runs separate display links for updating the main and mirror windows
Correctly handle updates to NSOpenGLContext's drawable object