(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.)

driver.c

@@ -0,0 +1,133 @@
+#include "stdafx.h"
+#include "openttd.h"
+#include "driver.h"
+#include "functions.h"
+#include "hal.h"
+#include "string.h"
+
+typedef struct {
+	const DriverDesc *descs;
+	const char *name;
+	void *var;
+} DriverClass;
+
+static DriverClass _driver_classes[] = {
+	{_video_driver_descs, "video", &_video_driver},
+	{_sound_driver_descs, "sound", &_sound_driver},
+	{_music_driver_descs, "music", &_music_driver},
+};
+
+enum {
+	DF_PRIORITY_MASK = 0xF,
+};
+
+static const DriverDesc* GetDriverByName(const DriverDesc* dd, const char* name)
+{
+	for (; dd->name != NULL; dd++) {
+		if (strcmp(dd->name, name) == 0) return dd;
+	}
+	return NULL;
+}
+
+static const DriverDesc* ChooseDefaultDriver(const DriverDesc* dd)
+{
+	byte os_version = GetOSVersion();
+	const DriverDesc *best = NULL;
+	int best_pri = -1;
+
+	for (; dd->name != NULL; dd++) {
+		if ((int)(dd->flags & DF_PRIORITY_MASK) > best_pri && os_version >= (byte)dd->flags) {
+			best_pri = dd->flags & DF_PRIORITY_MASK;
+			best = dd;
+		}
+	}
+	return best;
+}
+
+void LoadDriver(int driver, const char *name)
+{
+	const DriverClass *dc = &_driver_classes[driver];
+	const DriverDesc *dd;
+	const void **var;
+	const void *drv;
+	const char *err;
+	char *parm;
+	char buffer[256];
+	const char *parms[32];
+
+	parms[0] = NULL;
+
+	if (!*name) {
+		dd = ChooseDefaultDriver(dc->descs);
+	} else {
+		// Extract the driver name and put parameter list in parm
+		ttd_strlcpy(buffer, name, sizeof(buffer));
+		parm = strchr(buffer, ':');
+		if (parm) {
+			uint np = 0;
+			// Tokenize the parm.
+			do {
+				*parm++ = 0;
+				if (np < lengthof(parms) - 1)
+					parms[np++] = parm;
+				while (*parm != 0 && *parm != ',')
+					parm++;
+			} while (*parm == ',');
+			parms[np] = NULL;
+		}
+		dd = GetDriverByName(dc->descs, buffer);
+		if (dd == NULL)
+			error("No such %s driver: %s\n", dc->name, buffer);
+	}
+	var = dc->var;
+	if (*var != NULL) ((const HalCommonDriver*)*var)->stop();
+	*var = NULL;
+	drv = dd->drv;
+
+	err = ((const HalCommonDriver*)drv)->start(parms);
+	if (err != NULL)
+		error("Unable to load driver %s(%s). The error was: %s\n", dd->name, dd->longname, err);
+	*var = drv;
+}
+
+
+static const char* GetDriverParam(const char* const* parm, const char* name)
+{
+	uint len = strlen(name);
+
+	for (; *parm != NULL; parm++) {
+		const char* p = *parm;
+
+		if (strncmp(p, name, len) == 0) {
+			if (p[len] == '=')  return p + len + 1;
+			if (p[len] == '\0') return p + len;
+		}
+	}
+	return NULL;
+}
+
+bool GetDriverParamBool(const char* const* parm, const char* name)
+{
+	return GetDriverParam(parm, name) != NULL;
+}
+
+int GetDriverParamInt(const char* const* parm, const char* name, int def)
+{
+	const char* p = GetDriverParam(parm, name);
+	return p != NULL ? atoi(p) : def;
+}
+
+
+void GetDriverList(char* p)
+{
+	const DriverClass* dc;
+
+	for (dc = _driver_classes; dc != endof(_driver_classes); dc++) {
+		const DriverDesc* dd;
+
+		p += sprintf(p, "List of %s drivers:\n", dc->name);
+		for (dd = dc->descs; dd->name != NULL; dd++) {
+			p += sprintf(p, "%10s: %s\n", dd->name, dd->longname);
+		}
+	}
+}