domain: pass "domain" path to major registration
util.h: check for integer overflows

For very large values of item->size, item can actually wrap around and
its pointer can become smaller than head.
connection: re-order kdbus_conn members
policy: allow name ownership for bus creator

... and send permission between connections from the same user.
policy: drop KDBUS_CMD_EP_POLICY_SET (ABI breakage)

Drop KDBUS_CMD_EP_POLICY_SET. The new policy model will attach the items
to kdbus_cmd_make structs for the HELLO, CONN_UPDATE and MAKE_EP ioctls.

Hence, drop the entire KDBUS_CMD_EP_POLICY_SET for now, along with the
test code.
policy: factor out lookup code

Use this code to check for duplicates in the db from
kdbus_cmd_policy_set().
policy: rename item types to match new model (ABI break)

The new policy model has three levels of permissions:

 * SEE: A name may be seen on the bus
 * TALK: A name may be talked to (implies SEE)
 * OWN: A name may be owned (implies TALK and SEE)

This commit adopts these new levels, but doesn't actually implement
them yet.
policy: drop _db in some function names
policy: clean up comments and indent
policy: rework API

Rework the API exposed in policy.h, and make it base on kdbus_items.

Also, add some basic code for wildcard handling. This isn't tested at
all yet.
test: indentation fix
test: rename connect_to_bus → kdbus_hello
test: add test helpers to create activator connections

The new helper also supports uploading policy entries in the hello
ioctl.
test: drop dead policy helpers
policy: add dump function

(can be removed eventually)
policy: fix function name

The function is called kdbus_policy_check_talk_access() now.
connection: create policy db on demand
policy: pass flag to allow wildcards

Also, use the more generic KDBUS_ITEM_NAME instead of KDBUS_ITEM_POLICY_NAME.
policy: rename 'bits' to 'access' (ABI break)

Access types are now handled as levels rather than bitmasks:

 * An permission to OWN will implicitly allow TALK and SEE as well
 * An permission to TALK will implicitly allow SEE as well
connection: check for the size of the instance, not the type

That's just shorter and saves one line of code. No functional change.