output of fmt has changed for %g

R=rsc
DELTA=1  (0 added, 0 deleted, 1 changed)
OCL=19909
CL=19909

test/fmt_test.go

@@ -52,7 +52,7 @@ func main() {
 	E(f.s("\tf   ").f64(1234.5678e-8), "\tf   0.000012");
 	E(f.s("\tf   ").f64(-7.0), "\tf   -7.000000");
 	E(f.s("\tf   ").f64(-1e-9), "\tf   -0.000000");
-	E(f.s("\tg   ").g64(1234.5678e3), "\tg   1234567.8");
+	E(f.s("\tg   ").g64(1234.5678e3), "\tg   1.2345678e+06");
 	E(f.s("\tg   ").g64(1234.5678e-8), "\tg   1.2345678e-05");
 	E(f.s("\tg   ").g64(-7.0), "\tg   -7");
 	E(f.s("\tg   ").g64(-1e-9), "\tg   -1e-09");