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/IOSource.h

@@ -0,0 +1,73 @@
+// See the file "COPYING" in the main distribution directory for copyright.
+
+#ifndef IOSOURCE_IOSOURCE_H
+#define IOSOURCE_IOSOURCE_H
+
+#include <string>
+
+#include "Timer.h"
+
+namespace iosource {
+
+/**
+ * Interface class for components providing/consuming data inside Bro's main loop.
+ */
+class IOSource {
+public:
+	IOSource()	{ idle = closed = false; }
+	virtual ~IOSource()	{}
+
+	// Returns true if source has nothing ready to process.
+	bool IsIdle() const	{ return idle; }
+
+	// Returns true if more data is to be expected in the future.
+	// Otherwise, source may be removed.
+	bool IsOpen() const	{ return ! closed; }
+
+	// XXX
+	virtual void Init()	{ }
+
+	// XXX
+	virtual void Done()	{ }
+
+	// Returns select'able fds (leaves args untouched if we don't have
+	// selectable fds).
+	virtual void GetFds(int* read, int* write, int* except) = 0;
+
+	// The following two methods are only called when either IsIdle()
+	// returns false or select() on one of the fds indicates that there's
+	// data to process.
+
+	// Returns timestamp (in global network time) associated with next
+	// data item.  If the source wants the data item to be processed
+	// with a local network time, it sets the argument accordingly.
+	virtual double NextTimestamp(double* network_time) = 0;
+
+	// Processes and consumes next data item.
+	virtual void Process() = 0;
+
+	// Returns tag of timer manager associated with last processed
+	// data item, nil for global timer manager.
+	virtual TimerMgr::Tag* GetCurrentTag()	{ return 0; }
+
+	// Returns a descriptual tag for debugging.
+	virtual const char* Tag() = 0;
+
+protected:
+	// Derived classed are to set this to true if they have gone dry
+	// temporarily.
+	void SetIdle(bool is_idle)	{ idle = is_idle; }
+		
+
+	// Derived classed are to set this to true if they have gone dry
+	// temporarily.
+	void SetClosed(bool is_closed)	{ closed = is_closed; }
+
+private:
+	bool idle;
+	bool closed;
+};
+
+}
+
+#endif