Cleanup/improve PList usage and Event API

Majority of PLists are now created as automatic/stack objects,
rather than on heap and initialized either with the known-capacity
reserved upfront or directly from an initializer_list (so there's no
wasted slack in the memory that gets allocated for lists containing
a fixed/known number of elements).

Added versions of the ConnectionEvent/QueueEvent methods that take
a val_list by value.

Added a move ctor/assign-operator to Plists to allow passing them
around without having to copy the underlying array of pointers.

src/DFA.h

@@ -111,9 +111,6 @@ private:
 	PDict(CacheEntry) states;
 };
 
-declare(PList,DFA_State);
-typedef PList(DFA_State) DFA_state_list;
-
 class DFA_Machine : public BroObj {
 public:
 	DFA_Machine(NFA_Machine* n, EquivClass* ec);