lib, bgpd: Remove 'struct fifo' from lib/zebra.h

The 'struct fifo' and it's accompanying #defines do not
belong in lib/zebra.h.  Move them into their own header.

Signed-off-by: Donald Sharp <sharpd@cumulusnetworks.com>
diff --git a/lib/Makefile.am b/lib/Makefile.am
index ac51fc6..57e859d 100644
--- a/lib/Makefile.am
+++ b/lib/Makefile.am
@@ -28,7 +28,7 @@
 	str.h stream.h table.h thread.h vector.h version.h vty.h zebra.h \
 	plist.h zclient.h sockopt.h smux.h md5.h if_rmap.h keychain.h \
 	privs.h sigevent.h pqueue.h jhash.h zassert.h memtypes.h \
-	workqueue.h route_types.h libospf.h vrf.h
+	workqueue.h route_types.h libospf.h vrf.h fifo.h
 
 noinst_HEADERS = \
 	plist_int.h