The test performs implicit autolaunching of a bus
and checks if it is connectible.

In build the test is moved from "only non-windows with have_dbus_daemon"
to "anywhere".

This is intentional: actually it doesn't execute any external
binaries on unix (so doesn't require dbus_daemon)
and now has win32 implementation.

The test has some problems that are not problems of test itself,
but are reasoned by current win32 implementation:

 - since the implementation uses global win32 kernel objects
with fixed names not depending on g_get_user_runtime_dir or other context
if preexisting bus running by some other libgio-using application
the test would silently pass.

 - since the implementation uses problematic time-based synchronization,
that has a race condition between opening and reading mmaped address,
the test may randomly fail (I'd not seen this in practice).

 - since the implementation autolaunched process works for 3 seconds
after last client disconnects, the executed subprocess runs for 3 seconds
after test exit, maybe locking the libgio-2.0-0.dll file for that time.