Using sequential constants for *_FLOOD constants means that we can use a simple lookup table to convert them
into text for display and IGNORE_* constants.
This adds a FLOOD_FLAG() macro to convert a _FLOOD constant to the appropriate flag. For now this just
casts the argument to unsigned int.
Rename Flooding.type to Flooding.flags and change it to unsigned int, to reflect that it's a bitfield of
flags for multiple flooding types.
All callers of flood_prot() were supplying { get_flood_types(flood_type), flood_type } as the second and third arguments,
except one that supplied { get_flood_types(CTCP_FLOOD), CTCP_ACTION_FLOOD }.
Hardwiring this logic in to flood_prot() lets us remove the 'type' argument without changing the behaviour.
