Kernel route syncer supports multiple tables.

The changes are just too extensive for lazy me to list them
there, but see the comment at the top of sysdep/unix/krt.c.
The code got a bit more ifdeffy than I'd like, though.

Also fixed a bunch of FIXME's and added a couple of others. :)

doc/bird.conf.example

@@ -32,6 +32,7 @@ protocol kernel {
 #	async off;		# Netlink: Disable asynchronous events
 #	import none;		# Default is import all
 	export all;		# Default is export none
+#	kernel table 5;		# Kernel table to synchronize with (default: main)
 }
 
 protocol device {