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) 1997 by Radford M. Neal