[PATCH 0/5] A config option to compile out some namespaces code (v3)

[Pavel Emelyanov <xemul-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org>]

There were some questions like "do I need this on my cellphone"
in reply to different namespaces patches. Indeed, the namespaces
are not useful for most of the embedded systems, but the code
creating and releasing them weights a lot.

So I propose to add a config option which will help embedded
people to reduce the vmlinux size. This option simply compiles
out the namespaces cloning and releasing code *only*, but keeps
all the other logic untouched (e.g. the notion of init_ns).

When someone tries to clone some namespace with their support
turned off, he will receive an EINVAL error.

This patchset can save more than 2KB from the vmlinux when
turning the config option "NAMESPACES" to "n".

I do not introduce the NAMESPACES_EXPERIMENTAL config option, that
switches all the namespaces we consider experimental, but each 
namespace has its own config that can be mrked with "depends on
EXPERIMENTAL" on demand.

This is mainly done because some people consider pid namespaces broken
ant will probably want to make them depend on BROKEN. In this case
we'll have to introduce the NAMESPACES_BROKEN option which is not that
good.

Signed-off-by: Pavel Emelyanov <xemul-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org>