Backport of this xorg-xserver upstream patch:

  commit 20c2a3bcb11b5baf564e2c73a477ba23f5ae2b10
  Author: Peter Harris <pharris@opentext.com>
  Date:   Mon Jul 15 19:44:29 2013 -0400

    mi: Avoid stack smash when drawing dashed lines

    X.org Bug 54013 <https://bugs.freedesktop.org/show_bug.cgi?id=54013>
Reviewed-by: Adam Jackson <ajax@redhat.com>
Signed-off-by: Peter Harris <pharris@opentext.com>