[bgpd] Implement 'debug bgp zebra' to log all messages to and from zebra.

[bgpd] Implement 'debug bgp zebra' to log all messages to and from zebra.

2006-11-30 Andrew J. Schorr <ajschorr@alumni.princeton.edu>

	* bgp_debug.h: Declare new bgp_debug_zebra conf and term flags,
	  and define BGP_DEBUG_ZEBRA.
	* bgp_debug.c: Declare conf_bgp_debug_zebra and term_bgp_debug_zebra.
	  (debug_bgp_zebra, no_debug_bgp_zebra, undebug_bgp_zebra) New
	  functions to enable/disable bgp zebra debugging.
	  (no_debug_bgp_all) Turn off zebra debugging.
	  (show_debugging_bgp) Show whether zebra debugging is on.
	  (bgp_config_write_debug) Add 'debug bgp zebra' if configured.
	  (bgp_debug_init) Add new zebra debugging commands.
	* bgp_zebra.c: (bgp_router_id_update, bgp_interface_add,
	  bgp_interface_delete, bgp_interface_up, bgp_interface_down,
	  bgp_interface_address_add, bgp_interface_address_delete,
	  zebra_read_ipv4, zebra_read_ipv6, bgp_zebra_announce,
	  bgp_zebra_withdraw, bgp_redistribute_set, bgp_redistribute_unset)
	  If zebra debugging is enabled, log an appropriate debug message.