[BUILD] do not build rbtree anymore

Rbtree is not used anymore. Remove it from the makefiles.
diff --git a/Makefile.bsd b/Makefile.bsd
index 27efe89..d125c90 100644
--- a/Makefile.bsd
+++ b/Makefile.bsd
@@ -87,7 +87,7 @@
        src/time.o src/fd.o src/regex.o src/cfgparse.o src/server.o \
        src/checks.o src/queue.o src/capture.o src/client.o src/proxy.o \
        src/proto_http.o src/stream_sock.o src/appsession.o src/backend.o \
-       src/session.o src/hdr_idx.o src/rbtree.o src/ev_select.o src/ev_poll.o \
+       src/session.o src/hdr_idx.o src/ev_select.o src/ev_poll.o \
        src/ev_kqueue.o
 
 all: haproxy