lib: update ce-mask to uint64_t

lib: update ce-mask to uint64_t

lib/route/link.c already defines 32 attributes which fills the current
uint32_t used for ce_mask. To accommodate more attributes the mask needs
to be expanded. This patch updates the definition to uint64_t.

The nl_object_diff API is maintained for ABI with existing users. A new
nl_object_diff64 API is added for the expanded attribute list. The MSB
of the 32-bit API is used to indicate if higher order attributes had a
mismatch. (Suggested by Thomas).

Note that LINK_ATTR_LINK_NETNSID changes. But since the attribute flags
are not public API it shouldn't be a problem.

http://lists.infradead.org/pipermail/libnl/2015-December/002078.html
http://lists.infradead.org/pipermail/libnl/2015-December/002083.html

Signed-off-by: David Ahern <dsa@cumulusnetworks.com>
Signed-off-by: Thomas Haller <thaller@redhat.com>