Document missing wxGrid methods

Add documentation for the previously undocumented
IsCellEditControlShown(), Deselect{Col,Row,Cell}() and SetAttr().

See https://github.com/wxWidgets/wxWidgets/pull/405

(cherry picked from commit b1fd65a903)

interface/wx/grid.h

@@ -2722,6 +2722,13 @@ public:
     */
     bool IsCellEditControlEnabled() const;
 
+    /**
+        Returns @true if the in-place edit control is currently shown.
+
+        @see HideCellEditControl()
+    */
+    bool IsCellEditControlShown() const;
+
     /**
         Returns @true if the current cell is read-only.
 
@@ -3678,6 +3685,21 @@ public:
     */
     void ClearSelection();
 
+    /**
+        Deselects a row of cells.
+    */
+    void DeselectRow( int row );
+
+    /**
+        Deselects a column of cells.
+    */
+    void DeselectCol( int col );
+
+    /**
+        Deselects a cell.
+    */
+    void DeselectCell( int row, int col );
+
     /**
         Returns an array of individually selected cells.
 
@@ -4309,6 +4331,16 @@ public:
                  const wxGridCellCoords& bottomRight = wxGridCellCoords( -1, -1 ),
                  int style = wxGRID_DRAW_DEFAULT );
 
+    /**
+        Sets the cell attributes for the specified cell.
+
+        The grid takes ownership of the attribute pointer.
+
+        See the wxGridCellAttr class for more information about controlling
+        cell attributes.
+    */
+    void SetAttr(int row, int col, wxGridCellAttr *attr);
+
     /**
         Sets the cell attributes for all cells in the specified column.