encoding/binary: returns length of bool slice in intDataSize

intDataSize should return length of bool slice, so functions
Read and Write can use the fast path to process bool slice.

Change-Id: I8cd275e3ffea82024850662d86caca64bd91bf70
Reviewed-on: https://go-review.googlesource.com/112135Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>

src/encoding/binary/binary.go

@@ -665,6 +665,8 @@ func intDataSize(data interface{}) int {
 	switch data := data.(type) {
 	case bool, int8, uint8, *bool, *int8, *uint8:
 		return 1
+	case []bool:
+		return len(data)
 	case []int8:
 		return len(data)
 	case []uint8: