change utf8.FullRuneInString and utf8.DecodeRuneInString
to use single string argument instead of string, index.

R=r
DELTA=136  (9 added, 7 deleted, 120 changed)
OCL=28642
CL=28644
diff --git a/src/lib/fmt/print.go b/src/lib/fmt/print.go
index 229c264..66174c7 100644
--- a/src/lib/fmt/print.go
+++ b/src/lib/fmt/print.go
@@ -469,7 +469,7 @@
 	end := len(format) - 1;
 	fieldnum := 0;	// we process one field per non-trivial format
 	for i := 0; i <= end;  {
-		c, w := utf8.DecodeRuneInString(format, i);
+		c, w := utf8.DecodeRuneInString(format[i:len(format)]);
 		if c != '%' || i == end {
 			p.add(c);
 			i += w;
@@ -500,7 +500,7 @@
 		if i < end && format[i] == '.' {
 			p.fmt.prec, p.fmt.prec_present, i = parsenum(format, i+1, end);
 		}
-		c, w = utf8.DecodeRuneInString(format, i);
+		c, w = utf8.DecodeRuneInString(format[i:len(format)]);
 		i += w;
 		// percent is special - absorbs no operand
 		if c == '%' {