Fix type of the initial wxGrid selection event when dragging

Pass the same eventType ExtendCurrentBlock() is called with to
SelectBlock() called to perform the initial selection to ensure that
wxEVT_GRID_RANGE_SELECTING is sent while dragging instead of the
unexpected wxEVT_GRID_RANGE_SELECTED (in addition to the expected one
sent at the end when the drag is over).

src/generic/gridsel.cpp

@@ -526,7 +526,7 @@ bool wxGridSelection::ExtendCurrentBlock(const wxGridCellCoords& blockStart,
     // block to non-selected current cell.
     if ( !IsInSelection(m_grid->GetGridCursorCoords()) )
     {
-        SelectBlock(blockStart, blockEnd);
+        SelectBlock(blockStart, blockEnd, kbd, eventType);
         return true;
     }