BVG-INITIAL:  Set initial state for sampling from a bivariate Gaussian.

Usage:

    bvg-initial log-file value-1 value-2 { value-1 value-2 }

Writes a record with index 0 to the log file, containing the specified
values for the state variables (values after the first two are needed
only if replication was specified).

            Copyright (c) 1995-2003 by Radford M. Neal