I made a number of changes to the multi-pass CSG discretization to
improve performance. These include:

a) I increased the number of boundaries that can be handled from
   128 to 512.

b) I modified the discretization to perform the partitions against
   all the boundaries and then create a vtkDataSet at the end rather
   than creating a new vtkDataSet after partitioning with each boundary.

c) I changed the discretization to only process a portion of the mesh
   on each processor instead of the entire mesh. Previously each processor
   processed the entire mesh.



git-svn-id: http://visit.ilight.com/svn/visit/trunk/src@18840 18c085ea-50e0-402c-830e-de6fd14e8384