Boot in older VirtualBox is broken by syslinux 6

VirtualBox 4.1.18-dfsg-2+deb7u3: doesn’t boot at all from DVD (EFI mode doesn’t help). This was with an image built from commit e0a3c64
in feature/uefi. The same ISO boots fine in VirtualBox 4.3.10-dfsg-1~bpo70+1.

It seems to have been fixed in syslinux 6.03-pre5:

• http://bugzilla.syslinux.org/show_bug.cgi?id=45
• http://www.syslinux.org/archives/2014-April/021968.html
• http://www.syslinux.org/archives/2014-March/021782.html

Feature Branch: bugfix/7173-upgrade-syslinux

Related issues

• Blocked by #7173 (closed)

Original created by @intrigeri on 7232 (Redmine)