The Mesa state tracker as used by the Gallium3D hardware drivers has support for handling the creation of OpenGL 3.1 Core Profiles.
made on Wednesday is fairly basic since all of the OpenGL Core Profile plumbing was already done throughout Mesa. The OpenGL core profile is effectively a subset of the OpenGL compatibility profile where it doesn't expose deprecated portions of the API in later versions of OpenGL.
The Mesa commit doesn't implement OpenGL 3.1 on any new drivers but rather just allows for the Mesa state tracker to create a core profile when requested. If the utilized hardware driver can't support it, the request fails.