STYLE: Documenting the behavior of the IsInside() method when the argument

       region has zero size in any of its dimensions.

Author: Luis Ibanez

Code/Common/itkImageRegion.h

@@ -224,7 +224,10 @@ class ITK_EXPORT ImageRegion: public Region
     return true;
     }
 
-  /** Test if a region (the argument) is completely inside of this region */
+  /** Test if a region (the argument) is completely inside of this region. If
+   * the region that is passed as argument to this method, has a size of value
+   * zero, then it will not be considered to be inside of the current region,
+   * even its starting index is inside. */
   bool
   IsInside(const Self &region) const
     {