0025890: Intersection algorithm produces curves overlaped

1. Function IntImp_Int2S::ChangePoint() has been added (see cdl for detail information).
2. Attempt to forbidden break WLine if it goes along surface boundary.

Code optimization.

2nd optimization

Test case for issue CR25890

src/IntImp/IntImp_Int2S.cdl

@@ -225,7 +225,17 @@ is
 
     	is static;
     
+    ChangePoint(me: in out)
+      ---Purpose: return the intersection point which is 
+       --         enable for changing.
 
+        returns PntOn2S from IntSurf
+      ---C++: return &
+      ---C++: inline
+
+        is static;
+    
+    
 fields
 
     done         : Boolean from Standard;

src/IntImp/IntImp_Int2S.lxx

@@ -71,3 +71,7 @@ inline IntImp_TheFunction& IntImp_Int2S::Function()  {
   return myZerParFunc;
 } 
 
+inline IntSurf_PntOn2S& IntImp_Int2S::ChangePoint()
+{
+  return pint;
+}