[syslinux] isolinux failing on serial console

[Ady]

> 
> here's my config:
> 
> default menu.c32
> serial 0 115200
> # comment out to enable video console
> # console 0
> 
 
For testing with serial console purposes, I would suggest starting 
your cfg file with:

serial 0 115200
console 0
UI menu.c32

...

I mean, to use those directives as very first statements in your cfg 
file and in this same order.

One additional test could be to use Syslinux 4.06 binaries from 
kernel.org, without recompiling, but I'm not sure it would make any 
difference in this case.

 -Ady.