CVE request: DoS in multiple versions of GraphicsMagick

[Gustavo Grieco <gustavo.grieco () gmail com>]

We recently tested GraphicsMagick with our tool and found two issues that
causes DoS:

* Infinite loop caused by converting a circularly defined svg file.

* Arithmetic exception converting a svg file caused by a X%0 operation in
magick/render.c:3800

    (long) (y-fill_pattern->tile_info.y) % fill_pattern->rows,

Reproducers for both issues are attached. They are triggered by converting
a svg to another format. Identification is not affected.
These issues affect 1.3.18 and 1.3.23. Most likely other versions are
vulnerable too.

Regards,
Gustavo