Fix a bug (was not computing the last row & column using non-optimal method).

	* src/ComputeByParts.hxx: Here.
Added a mode to compute by parts with overlapping area.

	  * src/ComputeByPartsLinear.hh: Define the new class.
	  * src/ComputeByPartsLinear.hxx: Implements it.
	  * src/main.cc: Use it.