[AD] Bug with transparent ellipses

[Trent Gamblin <trentgamblin@xxxxxxxxxx>]

The following code segfaults in Linux with 4.2.0:

#include <allegro.h>

int main(void)
{
   allegro_init();
   set_gfx_mode(GFX_AUTODETECT_WINDOWED, 640, 480, 0, 0);
   BITMAP* bmp = create_bitmap(640, 480);
   drawing_mode(DRAW_MODE_TRANS, 0, 0, 0);
   ellipsefill(bmp, 0, 0, 10, 10, 0);
   drawing_mode(DRAW_MODE_SOLID, 0, 0, 0);
   destroy_bitmap(bmp);
   allegro_exit();
   return 0;
}


It looks like Allegro is not doing bounds checking, but it works fine if 
you remove
the drawing_mode calls. I haven't tested with other primitives. Also 
haven't tried this
4.3 so this may be fixed already.