lib, bgpd, tests: Refactor FILTER_X in zebra.h

lib/zebra.h has FILTER_X #define's.  These do not belong there.
Put them in lib/filter.h where they belong.

Signed-off-by: Donald Sharp <sharpd@cumulusnetworks.com>
diff --git a/bgpd/bgp_network.c b/bgpd/bgp_network.c
index 3c5e6c5..81a6a79 100644
--- a/bgpd/bgp_network.c
+++ b/bgpd/bgp_network.c
@@ -31,6 +31,7 @@
 #include "privs.h"
 #include "linklist.h"
 #include "network.h"
+#include "filter.h"
 
 #include "bgpd/bgpd.h"
 #include "bgpd/bgp_fsm.h"