Fix ABI compatibility

Fix ABI compatibility

Until we bump the SONAME to liblxc2, only symbol additions and struct
member additions are allowed.

Adding struct members in the middle of the struct breaks backward
compatibility.

This commit makes it clear when struct members were added and moves a
few members that were added in the middle of the 1.0 struct to the end
of it.

Note that unfortunately that means we're breaking backward compatibility
between LXC 1.1.0 and the state after this commit, given 1.1 is
reasonably new, this is the least damaging way of fixing the problem.

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>
Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>