Simplify a curve by combining compatible consecutive segments.

Input parameters:

1. Cr → Curve to simplify.
2. Mc → Merge consecutive collinear lines and co-circular arcs.
   •  True → Merge
   • False → Retain
3. Dt → Distance tolerance for simplification.
4. At → Angle tolerance for simplification.

Output parameters:

1. Cr → Simplified curve.