(svn r2685) -Codechange: Split the music/sound/video drivers into separate files and move them into subfolders.

This results in shorter and hopefully easier to maintain files.
Note: I had to change paths in #include statements of some unrelated files, because I added the ottd base directory to the include path (-I.)

video/null.c

@@ -0,0 +1,45 @@
+#include "stdafx.h"
+#include "openttd.h"
+#include "gfx.h"
+#include "variables.h"
+#include "video/null.h"
+#include "window.h"
+
+static void* _null_video_mem = NULL;
+
+static const char* NullVideoStart(const char* const* parm)
+{
+	_screen.width = _screen.pitch = _cur_resolution[0];
+	_screen.height = _cur_resolution[1];
+	_null_video_mem = malloc(_cur_resolution[0] * _cur_resolution[1]);
+	return NULL;
+}
+
+static void NullVideoStop(void) { free(_null_video_mem); }
+
+static void NullVideoMakeDirty(int left, int top, int width, int height) {}
+
+static int NullVideoMainLoop(void)
+{
+	uint i;
+
+	for (i = 0; i < 1000; i++) {
+		GameLoop();
+		_screen.dst_ptr = _null_video_mem;
+		UpdateWindows();
+	}
+
+	return ML_QUIT;
+}
+
+static bool NullVideoChangeRes(int w, int h) { return false; }
+static void NullVideoFullScreen(bool fs) {}
+
+const HalVideoDriver _null_video_driver = {
+	NullVideoStart,
+	NullVideoStop,
+	NullVideoMakeDirty,
+	NullVideoMainLoop,
+	NullVideoChangeRes,
+	NullVideoFullScreen,
+};