Fix off-by-one error with fast clahe

[minnerbe]

This PR fixes a minor off-by-one error of the "fast CLAHE" algorithm: the last column and row were not corrected before. I noticed this when correcting and reslicing a stack, which resulted in the last slice not being corrected.

This is a zoom-in of the lower right corner of the 'boats' image, treated with fast CLAHE (left) and normal CLAHE (right). Note the dark right and bottom pixels.

To reproduce, execute this:

final ImageJ ij = new ImageJ();
final ImagePlus imp = IJ.openImage("http://imagej.net/images/boats.gif");
imp.setRoi(26,20,668,543);
final ImagePlus cropped = imp.resize(668, 543, "bilinear");
cropped.setTitle("Original");
cropped.show();

final ImagePlus clahed = cropped.duplicate();
clahed.setTitle("CLAHE");
Flat.getInstance().run(clahed, 127, 256, 3.0f, null, false);
clahed.show();

final ImagePlus fastClahed = cropped.duplicate();
fastClahed.setTitle("Fast CLAHE");
Flat.getFastInstance().run(fastClahed, 127, 256, 3.0f, null, false);
fastClahed.show();

Tagging @axtimwalde and @StephanPreibisch for discussion.

[minnerbe]

Thanks, @axtimwalde ! You might want to hold off deploying if you planned on doing that, since I'm still working on another aspect of the CLAHE.