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/tests/bgp_capability_test.c b/tests/bgp_capability_test.c
index 3cfc198..a381351 100644
--- a/tests/bgp_capability_test.c
+++ b/tests/bgp_capability_test.c
@@ -25,6 +25,7 @@
 #include "stream.h"
 #include "privs.h"
 #include "memory.h"
+#include "filter.h"
 
 #include "bgpd/bgpd.h"
 #include "bgpd/bgp_open.h"