make: Generate crtools version from Makefile definition

This allows us to have a unique place where version lives
and what is more important other subsystems (such as docs
generation) may reuse version definitions.

At moment EXTRA (which corresponds kernels -rc tag) and
NAME is not yet used, but I desided to put them in place
for future needs.

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>