Merge branch 'grid-autosize-native-header'

Fix auto-sizing column labels when using native header in wxGrid.

See https://github.com/wxWidgets/wxWidgets/pull/1559

interface/wx/headerctrl.h

@@ -404,6 +404,16 @@ public:
      */
     int GetColumnTitleWidth(const wxHeaderColumn& col);
 
+    /**
+        Returns width needed for the column with the given index.
+
+        This is just a convenient wrapper for the overload taking
+        wxHeaderColumn.
+
+        @since 3.1.3
+     */
+    int GetColumnTitleWidth(unsigned int idx);
+
 protected:
     /**
         Method to be implemented by the derived classes to return the