llvmpipe multisample support extravaganza
This adds support for proper 4xMSAA to the llvmpipe codebase and surrounding pieces.
It adds support for window system multisampling, EXT_framebuffer_multisample, ARB_texture_multisample, ARB_sample_shading and ARB_shader_texture_image_samples, and mulitsample images.
It runs heaven and passes most of piglit.
Edited by Dave Airlie