strconv: fix internal documentation (clarification, typos)

Change-Id: I7514e643a6a81ca715adbf6f8d19d3b2dd43fe6c
Reviewed-on: https://go-review.googlesource.com/3810Reviewed-by: Alan Donovan <adonovan@google.com>

src/strconv/decimal.go

@@ -12,7 +12,7 @@
 package strconv
 
 type decimal struct {
-	d     [800]byte // digits
+	d     [800]byte // digits, big-endian representation
 	nd    int       // number of digits used
 	dp    int       // decimal point
 	neg   bool
@@ -105,7 +105,7 @@ func (a *decimal) Assign(v uint64) {
 // Signed int has 31 bits, and we have to be able to accommodate 9<<k.
 const maxShift = 27
 
-// Binary shift right (* 2) by k bits.  k <= maxShift to avoid overflow.
+// Binary shift right (/ 2) by k bits.  k <= maxShift to avoid overflow.
 func rightShift(a *decimal, k uint) {
 	r := 0 // read pointer
 	w := 0 // write pointer
@@ -228,7 +228,7 @@ func prefixIsLessThan(b []byte, s string) bool {
 	return false
 }
 
-// Binary shift left (/ 2) by k bits.  k <= maxShift to avoid overflow.
+// Binary shift left (* 2) by k bits.  k <= maxShift to avoid overflow.
 func leftShift(a *decimal, k uint) {
 	delta := leftcheats[k].delta
 	if prefixIsLessThan(a.d[0:a.nd], leftcheats[k].cutoff) {