MacOSX: Grid now is displayed correctly

    // Use a pixel based draw to display grid.  There are a lot of calls, so the cost is

    // high and grid is slowly drawn on some platforms.  Please note that this should

    // always be enabled until the bitmap based solution below is fixed.

#ifndef __WXMAC__

    GRSetColorPen( aDC, GetParent()->GetGridColor() );

#else

    // On mac (Cocoa), a point isn't a pixel and being of size 1 don't survive to antialiasing

    GRSetColorPen( aDC, GetParent()->GetGridColor(), aDC->DeviceToLogicalXRel(2) );

#endif

    int xpos;

    double right = ( double ) m_ClipBox.GetRight();