ovl: document lower layer ordering
ovl: document lower layer ordering

Reported-by: Fabian Sturm <f35f82cd4e9328fa97c0d07ea7c85126dbaa5212@aduu.de> 
Signed-off-by: Miklos Szeredi <84cd5483a2f9acd1c37251cba7c2908448f221b8@suse.cz>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs