package/upx: new package

UPX is a free, portable, extendable, high-performance executable
packer for several executable formats.

This is needed for syslinux 6.x.

Note: upx is a host-only package. Although it supports quite a few
target architectures, the only use so far will be for use by syslinux,
which already has an x86-on-x86 requirement anyway. So we currently do
not care to have target-dependencies on host-upx.

Signed-off-by: Frank Hunleth <fhunleth@troodon-software.com>
[yann.morin.1998@free.fr: builds fine in parallel; fix build to
 locate libucl; fix installation; don't add a menuconfig entry]
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Tested-by: Romain Naour <romain.naour@openwide.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>