MPI_WIN_SET_ERRHANDLER had their MPI handle parameters marked as INOUT
instead of IN, thereby disallowing passing pre-defined handles through
because they are constants (e.g., MPI_COMM_WORLD). This wasn't really
a problem for MPI_WIN_SET_ERRHANDLER since there are no predefined
windows, but it wasn't right.
This commit was SVN r23098.