Moved grayscale toggle code from C to ASM; enabled grayscale toggle in dos port

zsnes/src/linux/sdlintrf.asm

@@ -132,6 +132,7 @@ EXTSYM UDPDisableMode,UDPEnableMode,UDPClearVars,UDPWait1Sec
 EXTSYM WinErrorA2,WinErrorB2,WinErrorC2
 EXTSYM ZsnesPage
 EXTSYM GetLocalTime
+EXTSYM V8Mode,GrayscaleMode
 
 NEWSYM WinIntRFAsmStart
 
@@ -808,6 +809,12 @@ NEWSYM InitPreGame   ; Executes before starting/continuing a game
     call initwinvideo
     popad
 
+    mov al,[GrayscaleMode]
+    cmp al,[V8Mode]
+    je .nochangemode
+    xor byte[V8Mode],1
+.nochangemode
+
     mov byte[RaisePitch],1
     pushad
     call AdjustFrequency

zsnes/src/linux/sdllink.c

@@ -675,16 +675,12 @@ void Stop36HZ(void)
 DWORD FirstVid = 1;
 DWORD FirstFull = 1;
 extern BYTE GUIWFVID[];
-extern BYTE GrayscaleMode;
-extern BYTE V8Mode;
 void clearwin();
 
 void initwinvideo(void)
 {
 	DWORD newmode = 0;
 
-	V8Mode = (GrayscaleMode == 1);
-
 	if (CurMode != cvidmode)
 	{
 		CurMode = cvidmode;