[backwards] CodeDetector access.

By default, there is no code for Backwards.

Let the themers decide this one.

Themes/_fallback/metrics.ini

@@ -323,6 +323,8 @@ SaveScreenshot1=GetCodeForGame("SaveScreenshot1")
 SaveScreenshot2=GetCodeForGame("SaveScreenshot2")
 # on the player options menu.
 CancelAllPlayerOptions=GetCodeForGame("CancelAllPlayerOptions")
+# unused codes:
+Backwards=""
 # deprecated codes:
 NextTheme=""
 NextTheme2=""

src/CodeDetector.cpp

@@ -23,6 +23,7 @@ const char *CodeNames[] = {
 	"ModeMenu1",
 	"ModeMenu2",
 	"Mirror",
+	"Backwards",
 	"Left",
 	"Right",
 	"Shuffle",
@@ -200,6 +201,7 @@ bool CodeDetector::DetectAndAdjustMusicOptions( GameController controller )
 			switch( code )
 			{
 			case CODE_MIRROR:			po.ToggleOneTurn( PlayerOptions::TURN_MIRROR );		break;
+			case CODE_BACKWARDS:		po.ToggleOneTurn( PlayerOptions::TURN_BACKWARDS );	break;
 			case CODE_LEFT:				po.ToggleOneTurn( PlayerOptions::TURN_LEFT );		break;
 			case CODE_RIGHT:			po.ToggleOneTurn( PlayerOptions::TURN_RIGHT );		break;
 			case CODE_SHUFFLE:			po.ToggleOneTurn( PlayerOptions::TURN_SHUFFLE );	break;

src/CodeDetector.h

@@ -17,6 +17,7 @@ enum Code {
 	CODE_MODE_MENU1,
 	CODE_MODE_MENU2,
 	CODE_MIRROR,
+	CODE_BACKWARDS,
 	CODE_LEFT,
 	CODE_RIGHT,
 	CODE_SHUFFLE,