rename KDBUS_NAME_INFO to KDBUS_CONN_INFO

What that function does better fits into the connection context rather
than in the name lookup things, so move it around.

Also, while at it, fix up some comments and start using kernel-doc style
comments in kdbus.h.
kdbus.h: augment name_list API
pool: add kernel doc
names.h: kill left-over
add well known names of a connection in kdbus_cmd_conn_info()
connection: fix name attchment in kdbus_cmd_conn_info()
use owner_conn in kdbus_cmd_conn_info()
cosmetics
one more fixup in kdbus_cmd_conn_info()
one more fixup in kdbus_cmd_conn_info()
always reply with message from kdbus_cmd_conn_info()
allow mmap() only for connected file descriptors
use KDBUS_PART_HEADER to declare and initialize a single item header
cosmetics
split code in connection.c

factor out code from connection.c to handle.c to make the logic cleaner.
A 'handle' is something that can be turned into an ns owner, bus owner
or 'connection'.
handle: plug a potential memory leak
connection: cosmetics
names: add support for KDBUS_NAME_LIST_STARTERS_ONLY
straighten names API
metadata: add kernel doc