PK_ERROR_code_t    PK_BCURVE_combine
(
--- received arguments ---
int                n_bcurves,   --- number of bcurves ( >=2 )
PK_BCURVE_t        bcurves[],   --- bcurves

--- returned arguments ---
PK_BCURVE_t *const bcurve       --- resulting bcurve
)


This function creates a new bcurve by joining together a sequence of
bcurves.


Specific Errors:
    PK_ERROR_insufficient_curves    insufficient curves to join
    PK_ERROR_curves_dont_meet       curves not sequential
    PK_ERROR_bad_curves             invalid curves for joining


At least two B-curves must be supplied (n_bcurves >= 2).

The supplied curves must be in the correct order, and the end of each curve
(except the last) must coincide with the start of the next. The curves
must not be closed.

The end of the final curve may coincide with the start of the first, in
which case a closed B-curve will be made.

The supplied curves are unchanged by the operation.

The order of the resulting curve will be the maximum of the orders of the
supplied curves.

If any of the supplied curves are rational, the resulting curve will
be rational.