make: propagate config DEFINES in CFLAGS

The problem:
$(DEFINES) array added to $(CFLAGS) in a global Makefile.
But, in criu/Makefile we include Makefile.config, which
adds feature-based config options to $(DEFINES).
We need to propagate this new defines again to CFLAGS array.

Previously, I added:
ccflags-y		+= $(DEFINES)
to Makefile.crtools, but those $(DEFINES) are useful not only
in the crtools makefile.

Let's just propagate this feature defines to CFLAGS and DEFINES
in place.

Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
Reviewed-by: Cyrill Gorcunov <gorcunov@openvz.org>
Acked-by: Andrew Vagin <avagin@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>