attach names only when asked for
flush the dcache for the receiver's buffer only once at RECV
register all device numbers dynamically
kdbus.h: move ATTACH flags in hello cmd into own flags field

This allows us to let the flags start at bit 0, and eventually we can
re-use the enum at other places.
kdbus.h: add attach_flags to struct kdbus_cmd_name_info

This will be used in the future to tell kdbus which metadata to append.
bus, hello: generate unique bus identifier

Generate a random, unique bus identifier at bus creation time and copy
it back to the user in the HELLO ioctl.
generalize metadata attachment logic
rename
rename KDBUS_MSG_* to KDBUS_ITEM_*

This allows us to use that enums and items from other places.
enforce padding of the last item and an exact overall message size
rename manager to notify
metadata: fix indentation
connection: use bus pointer shortcut
README: update
names: make use of kdbus_meta in kdbus_cmd_name_query

The kdbus_meta structure allows us to append arbitrary data to the
answer to NAME_QUERY. That even makes to code shorter.
Makefile: let 'make tt' run test/test-kdbus as normal user
match: fix error unwind path
match: handle KDBUS_MATCH_NAME_* with empty strings
test: adjust bloom size
kdbus: add base ids