[zebra] Add test rig code, for testing the zebra RIB

[zebra] Add test rig code, for testing the zebra RIB

2006-07-27 Paul Jakma <paul.jakma@sun.com>

	* {ioctl,kernel}_null.c: Dummy/Null kernel method implementations,
	  useful for testing zebra code that calls such methods.
	* {redistribute,misc}_null.c: Dummy/Null methods, as above. But
	  for zclient, and for various misc functions.
	* test_main.c: Test harness for zebra, currently just to test the
	  RIB.
	* Makefile.am: Build testzebra using above.
	* zebra_rib.c: Add a global for the workqueue hold time, useful
	  for testing.