REORG: include: move lb_fwrr.h to haproxy/lb_fwrr{,-t}.h

Nothing fancy, includes were already OK. The proto didn't reference the
type, this was fixed. Still references proxy.h and server.h from types/.
diff --git a/include/types/backend.h b/include/types/backend.h
index 19a45f0..8a1f3bd 100644
--- a/include/types/backend.h
+++ b/include/types/backend.h
@@ -25,10 +25,10 @@
 #include <haproxy/lb_chash-t.h>
 #include <haproxy/lb_fas-t.h>
 #include <haproxy/lb_fwlc-t.h>
+#include <haproxy/lb_fwrr-t.h>
 #include <haproxy/api-t.h>
 #include <haproxy/thread.h>
 
-#include <types/lb_fwrr.h>
 #include <types/lb_map.h>
 #include <types/server.h>