broker integration: add bifs to inspect/manipulate broker data

i.e. script-layer functions to convert between bro values and broker
values; mostly for use w/ Bro's data store interface (coming soon).

scripts/base/frameworks/comm/main.bro

@@ -19,4 +19,9 @@ export {
 		name: string &optional;  # nil for invalid event/args.
 		args: vector of Comm::Data;
 	};
+
+	type Comm::TableItem : record {
+		key: Comm::Data;
+		val: Comm::Data;
+	};
 }