[syslinux] possible pxelinux.asm error

[stevea]

The syslinux-3.51 file pxelinux.asm appears to have an error in parsing 
dhcp options.

Line 2267  has code to parse  boot file names from the dhcp options:
           dopt 64, bootfile_name
                   mov di,BootFile
                   jmp dhcp_copyoption

however the correct rfc2132 option for the bootfile is decimal 67 and 
NOT 64.
The would seem to prevent some servers like dnsmasq from serving
this client.