bytes, strings: declare variables inside loop they're used in

The recently updated Count functions declare variables before
special-cased returns.

Change-Id: I8f726118336b7b0ff72117d12adc48b6e37e60ea
Reviewed-on: https://go-review.googlesource.com/39357
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/bytes/bytes.go

@@ -48,11 +48,11 @@ func explode(s []byte, n int) [][]byte {
 
 // countGeneric actually implements Count
 func countGeneric(s, sep []byte) int {
-	n := 0
 	// special case
 	if len(sep) == 0 {
 		return utf8.RuneCount(s) + 1
 	}
+	n := 0
 	for {
 		i := Index(s, sep)
 		if i == -1 {

src/strings/strings.go

@@ -75,11 +75,11 @@ func hashStrRev(sep string) (uint32, uint32) {
 // Count counts the number of non-overlapping instances of substr in s.
 // If substr is an empty string, Count returns 1 + the number of Unicode code points in s.
 func Count(s, substr string) int {
-	n := 0
 	// special case
 	if len(substr) == 0 {
 		return utf8.RuneCountInString(s) + 1
 	}
+	n := 0
 	for {
 		i := Index(s, substr)
 		if i == -1 {