Landing in the X.Org Server mainline Git repository this afternoon are implementations of GLX_ARB_create_context_profile, GLX_EXT_create_context_es2_profile, and GLX_ARB_create_context_robustness.
The GLX_ARB_create_context* work is what's used by OpenGL 3.0+ applications for specifying at context-creation time what OpenGL version and context properties it wishes to use. The now-supported GLX_ARB_create_context_profile extension is a requirement of OpenGL 3.2 and later.
The GLX_EXT_create_context_es2_profile extension is dependent upon OpenGL ES 2.0 and the just-mentioned GLX_ARB_create_context* extensions. The GLX_EXT_create_context_es2_profile is used for creating an OpenGL ES 2.0 context. Lastly, the GLX_ARB_create_context_robustness extension is used for creating an OpenGL context supporting robust buffer access behavior and a specified graphics reset notification behavior.
The patches now found in the mainline X.Org Server can be found from CGit. X.Org Server 1.13 is set for release in September, but unfortunately is unlikely to make it into Ubuntu 12.10.