clear flags so that %+v does not pass the +

to the first field it prints.

R=r
DELTA=2  (1 added, 0 deleted, 1 changed)
OCL=21324
CL=21328

src/lib/fmt/print.go

@@ -386,7 +386,8 @@ func (p *P) printField(field reflect.Value) (was_string bool) {
 		p.add('{');
 		v := field.(reflect.StructValue);
 		t := v.Type().(reflect.StructType);
-		donames := p.fmt.plus;	// first p.printField clears flag
+		donames := p.fmt.plus;
+		p.fmt.clearflags();	// clear flags for p.printField
 		for i := 0; i < v.Len();  i++ {
 			if i > 0 {
 				p.add(' ')