[syslinux] Append line size limit in syslinux 3.72

[H. Peter Anvin]

H. Peter Anvin wrote:
> 
> Wait... you're talking about RHEL4.  That must be a 2.6.9 kernel. 
> Either way, only kernels after 2.6.21 support more than 256 characters, 
> so I'm more than a bit confused about that.
> 

For what it's worth, I just tested out Syslinux 3.72 with a 
700-character APPEND statement, and it worked fine, at least in PXELINUX.

	-hpa