Proposal for the integration of a500 machine specific additions

Here are my modifications to integrate the a500 machine. It shouldn't have any impact on other machines, as all the additions have the "_a500" suffix.

There is one modification that should require a more careful look: I'm not sure if the way I propose the LSM patch is the best one. In this PR, I've added a patch file corresponding to the diff between my fork and the main webos branch. The patch is not big, but it modifies some source files, and may break in the future. I would be glad to include my LSM modifications in a better way, if you propose one.