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/Stmt.h

@@ -213,6 +213,9 @@ protected:
 	Stmt* s;
 };
 
+declare(PList,Case);
+typedef PList(Case) case_list;
+
 class SwitchStmt : public ExprStmt {
 public:
 	SwitchStmt(Expr* index, case_list* cases);