Windows provides OpenGL 1.1 with platform-specific extensions (WGL) in its
software implementation of OpenGL. The purpose of Mesa in this directory is to
provide an equivalent of that. In order to accomplish just this purpose, it is
based on Mesa 2.6 and not intended to be synchronized with recent versions.
See CORE-7499 for details.

If you look for a modern software OpenGL implemenation, a Mesa package with
the Gallium LLVMpipe driver is available on RAPPS.