GLEW and my shader disagree - do I have that extension or not?
opengl,glsl,glew,opengl-extensions
GL_ARB_robustness is not a GLSL modifying extension. The intention of this extension is to make the interaction with the OpenGL API more robust in the sense that out-of-bound accesses to memory can be caught. Somewhat like the difference between sprintf and snprintf. Since this is not a shader extension it...
GL_ARB_sparse_texture not supported
As genpfault said in the comment, only extensions that add features to the GLSL language need to be enabled manually in the shader with the #extension directive. Since GL_ARB_sparse_texture doesn't add GLSL functionality, you don't need to explicitly enable it in your shaders - checking support with glGetIntegerv is enough....