Avoid overriding tune files

Signed-off-by: Christopher Larson <chris_larson@mentor.com>
layer.conf: use expansion for BBFILES, not literals

Signed-off-by: Christopher Larson <chris_larson@mentor.com>
Update TODO

Signed-off-by: Christopher Larson <chris_larson@mentor.com>
tcmode: fix l-l-h pref to kill ppc warning

Signed-off-by: Christopher Larson <chris_larson@mentor.com>