boot/syslinux: bump version

This new version has a very, very weird build system. There are different
images that syslinux can now build:
  - the plain legacy-bios images we already supported previously
  - two new EFI32 and EFI64 applications

To build one or the other, the Makefile accepts one or more of:
    make (bios|efi32|efi64)

Specify all of them, and it builds all. Specify 'install', and it installs
all of them, as one may expect.

Still a regular behaviour, is to build only a subset (down to one):
    make bios           <-- builds just the legacy-bios images
    make efi32 bios     <-- builds just the legacy-bios and efi32 images

Where it gets weird is the install procedure. Can you guess how it's done?
Hint: the syslinux guys have invented the multiple-argument parsing in
pure Makefiles. To build then install only the bios images, one would do:
    make bios
    make bios install

Yep, that's it. make bios install. Two arguments, one action.

That makes for some funky workarounds in our install procedure...

'bios' is the only image we support so far, with efi to come in a future
patch.

Using MAKE1, as there are issues with highly-parallel builds.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Frank Hunleth <fhunleth@troodon-software.com>
Tested-by: Frank Hunleth <fhunleth@troodon-software.com>
Tested-by: Romain Naour <romain.naour@openwide.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>