overo.inc: resolve udev conflict with systemd

Alternative of using systemd was added for Angstrom, but full support is not
currently in denzil.

Signed-off-by: Peter A. Bigot <pab@pabigot.com>
gumstix-dsp-image: add

Based on material at http://www.sleepyrobot.com/?p=210.

omap3.inc change to match meta-ti; TARGET_ARCH is not needed.

overo.inc excludes unreferenced TOOLCHAIN_SYSPATH.

gumstix-dsp-image.bb from http://www.sleepyrobot.com/wp-content/uploads/2012/11/gumstix-dsp-image.bb

Note: ti-dmai fails to build with GNU make 3.82 due to a subtle bug in make;
using make 3.81 works.

Signed-off-by: Peter A. Bigot <pab@pabigot.com>
gumstix-console-image: support IMAGE_EXTRA_INSTALL

Was defaulted, but never added to the image making the feature useless.

FWIW, upstream standard is CORE_IMAGE_EXTRA_INSTALL but since this doesn't
use core-image there's no reason to use that variable.

Signed-off-by: Peter A. Bigot <pab@pabigot.com>
gumstix-dsp-image: revise to extend gumstix-console-image

No change in installed packages, just decouples the content.

Signed-off-by: Peter A. Bigot <pab@pabigot.com>