Since August there has been a branch that provides Clover, which is an OpenCL state tracker ("CL over [Gallium3D]"), but unlike other state trackers it hasn't been progressing at a brisk pace. In fact, the Mesa/Clover code has not been touched now in three months.
Fortunately though a developer had submitted patches today to the Mesa3D development list that creates and implements stub context methods in OpenCL. The implemented methods were clCreateContext, clCreateContexFromType, clRetainContext, and clReleaseContext.
Zack Rusin has now chimed in on the mailing list with a few questions/statements surrounding OpenCL in Mesa / Gallium3D. There are a few issues that need to be decided upon for implementing compute support in Gallium3D, which comes down to whether this state tracker should live within Mesa or its own repository, what build system to use for Clover (cmake or scons), and the language selection to provide for OpenCL support. This discussion is ongoing and we will be monitoring this mailing list thread.