overo.inc: resolve udev conflict with systemd

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>