IOSource reorg.

A bunch of infrastructure work to move IOSource, IOSourceRegistry (now
iosource::Manager) and PktSrc/PktDumper code into iosource/, and over
to a plugin structure.

Other IOSources aren't touched yet, they are still in src/*.

It compiles and does something with a small trace, but that's all I've
tested so far. There are quite certainly a number of problems left, as
well as various TODOs and cleanup; and nothing's cast in stone yet.

Will continue to work on this.

src/iosource/Component.h

@@ -0,0 +1,56 @@
+// See the file "COPYING" in the main distribution directory for copyright.
+
+#ifndef IOSOURCE_PLUGIN_COMPONENT_H
+#define IOSOURCE_PLUGIN_COMPONENT_H
+
+#include "plugin/Component.h"
+
+namespace iosource {
+
+class IOSource;
+
+/**
+ * Component description for plugins providing IOSources.
+ */
+class Component : public plugin::Component {
+public:
+	typedef IOSource* (*factory_callback)();
+
+	/**
+	 * XXX
+	 */
+	Component(const std::string& name);
+
+	/**
+	 * Copy constructor.
+	 */
+	Component(const Component& other);
+
+	/**
+	 * Destructor.
+	 */
+	~Component();
+
+	/**
+	 * XXX
+	 */
+	virtual const char* Name() const	{ return name.c_str(); }
+
+	/**
+	 * Generates a human-readable description of the component. This goes
+	 * into the output of \c "bro -NN".
+	 */
+	virtual void Describe(ODesc* d) const;
+
+	Component& operator=(const Component& other);
+
+protected:
+	Component(plugin::component::Type type, const std::string& name);
+
+private:
+	std::string name;
+};
+
+}
+
+#endif