v 5.1.0 is a bug fix release.
fixes #2685 "Clicking "Manage Members" in a vlan subinterface of a cluster causes crash".
fixed SF bug #3468358 "change in rule-compilation between 5.0.0 and 5.0.1". Rule with cluster interface in "Destination" should compile into matching ip addresses assigned to the cluster interface object and corresponding member firewall's interface object, but in v5.0.1 it only matched member interface address. This bug triggered when iptables version was set to 1.2.11 or greater. This was a regression from v5.0.0
fixes #2686 "automatic rules for heartbeat are not generated for vlan subinterfaces"
fix for SF bug #3468802. Need to define macro __STDC_FORMAT_MACROS. This still needs to be tested on all build machines.