Fix making the wrong wxGrid cell visible when selecting

We should make visible the cell of the corner of the current selected block.

Also fix names of the wxGrid::UpdateBlockBeingSelected parameters because
actually passed сщщквы are of any opposite selection block corners.

include/wx/generic/grid.h

@@ -2325,13 +2325,13 @@ protected:
 
     // this function is called to extend the block being currently selected
     // from mouse and keyboard event handlers
-    void UpdateBlockBeingSelected(int topRow, int leftCol,
-                                  int bottomRow, int rightCol);
+    void UpdateBlockBeingSelected(int blockStartRow, int blockStartCol,
+                                  int blockEndRow, int blockEndCol);
 
-    void UpdateBlockBeingSelected(const wxGridCellCoords& topLeft,
-                        const wxGridCellCoords& bottomRight)
-        { UpdateBlockBeingSelected(topLeft.GetRow(), topLeft.GetCol(),
-                         bottomRight.GetRow(), bottomRight.GetCol()); }
+    void UpdateBlockBeingSelected(const wxGridCellCoords& blockStart,
+                                  const wxGridCellCoords& blockEnd)
+        { UpdateBlockBeingSelected(blockStart.GetRow(), blockStart.GetCol(),
+                                   blockEnd.GetRow(), blockEnd.GetCol()); }
 
     virtual bool ShouldScrollToChildOnFocus(wxWindow* WXUNUSED(win)) wxOVERRIDE
         { return false; }