virdbus: don't force users to pass int for bool values

virdbus: don't force users to pass int for bool values

Use of an 'int' to represent a 'bool' value is confusing.  Just
because dbus made the mistake of cementing their 4-byte wire
format of dbus_bool_t into their API doesn't mean we have to
repeat the mistake.  With a little bit of finesse, we can
guarantee that we provide a large-enough value to the DBus
code, while still copying only the relevant one-byte bool
to the client code, and isolate the rest of our code base from
the DBus stupidity.

* src/util/virdbus.c (GET_NEXT_VAL): Add parameter.
(virDBusMessageIterDecode): Adjust all clients.
* src/util/virpolkit.c (virPolkitCheckAuth): Use nicer type.
* tests/virdbustest.c (testMessageSimple, testMessageStruct):
Test new behavior.

Signed-off-by: Eric Blake <eblake@redhat.com>