Bug#823750: PSD heap overflow

[Bastien ROUCARIES]

   Fix a heap buffer overflow in psd file handling

    Bug: https://github.com/ImageMagick/ImageMagick/issues/92.
    Origin: 
https://github.com/ImageMagick/ImageMagick/commit/30eec879c8b446b0ea9a3bb0da1a441cc8482bc4
    Bug-ubuntu:
https://bugs.launchpad.net/ubuntu/+source/imagemagick/+bug/1537418
    Bug-debian: https://bugs.debian.org/823750