cache_mngr: add include callback v2

cache_mngr: add include callback v2

This patch adds change_func_v2_t to add a more detailed callback in
case of a cache change. The change function is registered using the new
nl_cache_mngr_add_cache_v2. In case the new change function is set,
nl_cache_include_v2 and thus cache_include_v2 will be used to perform the cache
inclusion.

The parameter of change_func_v2_t are the following:
* struct nl_cache * => cache
* struct nl_object * => the old/deleted nl_object
* struct nl_object * => the new nl_object
* uint64_t => the result of nl_object_diff64 in case of a change
* int => NL_ACT_*
* void * => data

https://github.com/thom311/libnl/issues/71
http://lists.infradead.org/pipermail/libnl/2016-September/002214.html
http://lists.infradead.org/pipermail/libnl/2016-October/002229.html
http://lists.infradead.org/pipermail/libnl/2016-November/002250.html