[Png-mng-security] Potential denial of service attack in lcms-1.17

[glennrp at comcast.net]

John, if you will provide a patch I'll be happy to reformat
it according to mozilla requirements and run it through
their process.

Also I'll port the libpng-1.4.x patch back into 1.0.x/1.2.x
if you are satisfied with it.

Glenn