games/gba: fix -3 crash and prevent >100% speed

sys/src/games/gba/dat.h

@@ -141,6 +141,8 @@ enum {
 	KB = 1024,
 	BACKTYPELEN = 64,
 	HZ = 16777216,
+	MILLION = 1000000,
+	BILLION = 1000000000,
 };
 
 typedef struct Var Var;

sys/src/games/gba/gba.c

@@ -317,6 +317,8 @@ flush(void)
 	extern uchar pic[];
 	Mouse m;
 	int x;
+	static vlong old, delta;
+	vlong new, diff;
 
 	if(nbrecvul(mc->resizec) > 0){
 		if(getwindow(display, Refnone) < 0)
@@ -347,7 +349,20 @@ flush(void)
 	flushimage(display, 1);
 	if(profile)
 		timing();
-	audioout();
+	if(audioout() < 0){
+		new = nsec();
+		diff = 0;
+		if(old != 0){
+			diff = BILLION/60 - (new - old) - delta;
+			if(diff >= MILLION)
+				sleep(diff/MILLION);
+		}
+		old = nsec();
+		if(diff != 0){
+			diff = (old - new) - (diff / MILLION) * MILLION;
+			delta += (diff - delta) / 100;
+		}
+	}
 	if(framestep){
 		paused = 1;
 		qlock(&pauselock);

sys/src/games/gba/ppu.c

@@ -754,7 +754,8 @@ hblanktick(void *)
 			setif(IRQVCTR);
 	}else{
 		syncppu(240);
-		linecopy();
+		if(ppuy < 160)
+			linecopy();
 		addevent(&evhblank, 68*4);
 		hblank = 1;
 		if((stat & IRQHBLEN) != 0)