0025715: Intersection between cylinders produces excess vertices

0025715: Intersection between cylinders produces excess vertices

1. Curve boundaries were more precised.
2. Some test cases were changed in accordance of their new behavior.
3. Code fragment for WLines joining was moved to higher level (for more universal using in the future).

Code was changed in accordance with the last remark.

Added test cases bugs/modalg_5/bug25715_1 bug25715_2 bug25715_3