- dbus/dbus-bus.c
(internal_bus_get): new method that take over the heavy lifting
of dbus_bus_get and adds the ability to get a private connection
to the bus
(dbus_bus_get): wrapper to internal_bus_get that provides the same
interface as in previous versions
(dbus_bus_get_private): new method that is a wrapper to
internal_bus_get to get a private connection to the bus

- dbus/dbus-bus.h
(dbus_bus_get_private): add as a public libdbus interface

- dbus-1.pc.in: output system_bus_default_address and
sysconfdir variables so apps can use them when compiling