Introduces the functions genl_register_family() and
genl_unregister_family() to register a Generic Netlink family
which does not implement a cachable type.
API users can direct received messages into genl_handle_msg() which
will validate the messages and call the callback functions defined
in the commands definition.
See test/test-genl.c for an example on how to use it.
Let the user specify a list of cache types to add to the manager
as arguments instead of adding a static list.
Uses the newly added nl_cache_mngr_info() to constantly print
information about the manager.
Caches allocated by the cache manager must be freed again when the cache
manager itself is freed. However, the netlink socket is allocated
indepdently so it should not be freed.
Fixes an off-by-one when releasing local ports. Fixes nl_connect()
to properly close the socket upon failure. Return EBADFD if
operations are performed on unconnected sockets where appropriate.
Makes nl_handle_alloc() return an error if all local ports are
used up.
