Method for obtaining the survival function of a dfr_dist object.
      Source: R/dfr_dist.R
      surv.dfr_dist.RdMethod for obtaining the survival function of a dfr_dist object.
Arguments
- x
 The object to obtain the survival function of.
- ...
 Additional arguments to pass into the
cum_hazconstructor.
Value
A function that computes the survival function of the
distribution.
It accepts t, the time at which to compute the survival, par,
the parameters of the distribution, log.p argument that
determines whether to compute the log of the survival, and
it passes any additional arguments into the rate function of
the dfr_dist object x.