RCD border artifacts fixed.

Now 8 border pixels are used for interpolation in RCD as 4 caused
artifacts. Fixes #4225, patch by agriggio.

rtengine/demosaic_algos.cc

@@ -4213,7 +4213,7 @@ void RawImageSource::rcd_demosaic()
         }
     }
 
-    border_interpolate2(width, height, 4);
+    border_interpolate2(width, height, 8);
 
     if (plistener) {
         plistener->setProgress(1);