* bus/config-parser.c (bus_config_parser_unref): free
	list of mechanisms, bug discovered by test suite enhancements
	(putting system.conf and session.conf into suite)

	* test/Makefile.am, test/test-service.c: add placeholder for a
	test service that we'll activate as part of test suite. Doesn't
	do anything yet.

	* dbus/dbus-sysdeps.c (_dbus_setenv): support unsetenv by
	setting NULL value, and use system malloc not dbus_malloc()
	when we have unavoidable memleakage.

	* dbus/dbus-bus.c (dbus_bus_get): fix bug where bus type of 0
	didn't work, and support DBUS_BUS_ACTIVATION.

	* bus/activation.c (child_setup): pass our well-known bus type to
	the child

	* bus/config-parser.c: support <type> to specify well-known type

	* doc/dbus-specification.sgml: document the env variables to
	locate well-known buses and find service activator