accept c++-style comments for interoperability with
foreign code.

Reference: /n/sources/patch/applied/yacccmt
Date: Sat Nov 21 17:24:45 CET 2009
Signed-off-by: quanstro@quanstro.net

--- /sys/src/cmd/yacc.c	Sat Nov 21 17:23:24 2009
+++ /sys/src/cmd/yacc.c	Sat Nov 21 17:23:18 2009
@@ -1918,17 +1918,22 @@
 
 	/* i is the number of lines skipped */
 	i = 0;
-	if(Bgetrune(finput) != '*')
-		error("illegal comment");
 	c = Bgetrune(finput);
-	while(c != Beof) {
-		while(c == '*')
-			if((c=Bgetrune(finput)) == '/')
-				return i;
-		if(c == '\n')
-			i++;
-		c = Bgetrune(finput);
-	}
+	if(c == '/'){
+		while((c = Bgetrune(finput)) != Beof)
+			if(c == '\n')
+				return 1;
+	}else if(c == '*'){
+		while((c = Bgetrune(finput)) != Beof) {
+			while(c == '*')
+				if((c=Bgetrune(finput)) == '/')
+					return i;
+			if(c == '\n')
+				i++;
+		}
+	}else
+		error("illegal comment");
+
 	error("EOF inside comment");
 	return 0;
 }