make: insert Makefile.inc into Makefile

Makefile.inc is included only into Makefile now. So let's insert it's content
into Makefile itself.

Signed-off-by: Stanislav Kinsbursky <skinsbursky@openvz.org>
Looks-good-to: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>