[syslinux] EFI: HP + syslinux = crash [ brown paper bag update ]

[Patrick Masotta]

 >>>
 >
 Please implement these new changes over your last non-debug
 > working build (multi-nic fix) and let's see how it goes.
 >
 > https://github.com/ppatpat/syslinux/compare/master...ppatpat:zlib?expand=1
 >
 > Please report your results.
 
 Results are in. They are very good. 
 No crashing even with the original config!
 <<<

It is also working here; I think this particular PNG issue is fixed.

It's worth to mention that the replaced code looks valid to me; that's why I think 
this is probably some sort of compiler bug. It was really hard to find.
We should keep an eye on this issue; it might appear somewhere else.

Best,
Patrick