kbuild, deb-pkg: select userland architecture based on UTS_MACHINE

Instead of creating the debian package for the compiling userland,
create it for a userland matching the kernel thats being compiled.

This patch supports all Lenny release architectures,
and Linux-based architecture candidates for Squeeze.

If it can't find a proper Debian userspace it displays a warning,
and fallback to let deb-gencontrol use the host's userspace arch.

Eg. with this patch the following make command:

	make ARCH=i386 deb-pkg

will output an i386 Debian package instead of an amd64 one,
when run on an amd64 machine.

Signed-off-by: Asbjoern Sloth Toennesen <asbjorn@asbjorn.biz>
Acked-by: maximilian attems <max@stro.at>
Signed-off-by: Michal Marek <mmarek@suse.cz>