fix vietnamese telex state

vi.c

@@ -117,13 +117,16 @@ onsetglide(Str *m)
 Emit
 transvi(Im *im, Rune c)
 {
-	Emit e;
+	Emit e, mappedkey;
 	Str mapped, pre;
 	int i, tidx, vi, last, penult, glide;
 	Rune v, b1, b2;
 
 	if(!istone(c) && c != 'z')
 		return transmap(im, c);
+	mappedkey = transmap(im, c);
+	if(mappedkey.eat)
+		return mappedkey;
 
 	memset(&e, 0, sizeof e);
 	if(im->pre.n == 0)
@@ -182,3 +185,25 @@ transvi(Im *im, Rune c)
 	e.next = mapped;
 	return e;
 }
+
+void
+backvi(Im *im)
+{
+	Emit e;
+	Str raw;
+	int i;
+
+	if(im->raw.n == 0){
+		spopr(&im->pre);
+		return;
+	}
+	raw = im->raw;
+	spopr(&raw);
+	sclear(&im->pre);
+	for(i = 0; i < raw.n; i++){
+		e = transvi(im, raw.r[i]);
+		sclear(&im->pre);
+		sappend(&im->pre, &e.next);
+	}
+	im->raw = raw;
+}