Add opaque type to lexer, parser, and BroType.

src/Type.h

@@ -29,6 +29,7 @@ typedef enum {
 	TYPE_LIST,
 	TYPE_FUNC,
 	TYPE_FILE,
+	TYPE_OPAQUE,
 	TYPE_VECTOR,
 	TYPE_TYPE,
 	TYPE_ERROR
@@ -499,6 +500,24 @@ protected:
 	BroType* yield;
 };
 
+class OpaqueType : public BroType {
+public:
+	OpaqueType(const string& name);
+	virtual ~OpaqueType() { };
+
+	const string& Name()	{ return name; }
+
+	void Describe(ODesc* d) const;
+
+protected:
+	OpaqueType() { }
+
+  // TODO: Serialization semantics not yet defined.
+	//DECLARE_SERIAL(OpaqueType)
+
+	const string name;
+};
+
 class EnumType : public BroType {
 public:
 	EnumType(const string& arg_name);