* dbus/dbus-connection.c (_dbus_connection_queue_received_message_link,
_dbus_connection_message_sent,
_dbus_connection_send_preallocated_unlocked_no_update,
_dbus_connection_pop_message_link_unlocked): handle the case when path
is NULL when calling _dbus_verbose

* configure.in: check for functions getpeerucred and getpeereid

* dbus/dbus-sysdeps.c (_dbus_read_credentials_unix_socket): provides
support of auth EXTERNAL on Solaris 10+ (getpeerucred), FreeBSD 4.6+,
OpenBSD 3.0+ and FreeBSD 5.0+ as well as MacOSX 10.2+ (getpeereid).
Patch was only tested on Solaris 10 x86 so it might be issues
with other platforms (i.e. BSDs and MacOSX)