strconv: handle [-+]Infinity in atof

This is the form as returned by Postgres, as well
as JavaScript.

I've tried and failed to find authorative docs online
about the proper string serialization, if any.

R=golang-dev, gri, r, r, rsc
CC=golang-dev
https://golang.org/cl/4650077

src/pkg/strconv/atof.go

@@ -43,11 +43,13 @@ func special(s string) (f float64, ok bool) {
 	switch {
 	case equalIgnoreCase(s, "nan"):
 		return math.NaN(), true
-	case equalIgnoreCase(s, "-inf"):
+	case equalIgnoreCase(s, "-inf"),
+		equalIgnoreCase(s, "-infinity"):
 		return math.Inf(-1), true
-	case equalIgnoreCase(s, "+inf"):
-		return math.Inf(1), true
-	case equalIgnoreCase(s, "inf"):
+	case equalIgnoreCase(s, "+inf"),
+		equalIgnoreCase(s, "+infinity"),
+		equalIgnoreCase(s, "inf"),
+		equalIgnoreCase(s, "infinity"):
 		return math.Inf(1), true
 	}
 	return

src/pkg/strconv/atof_test.go

@@ -47,6 +47,9 @@ var atoftests = []atofTest{
 	{"inf", "+Inf", nil},
 	{"-Inf", "-Inf", nil},
 	{"+INF", "+Inf", nil},
+	{"-Infinity", "-Inf", nil},
+	{"+INFINITY", "+Inf", nil},
+	{"Infinity", "+Inf", nil},
 
 	// largest float64
 	{"1.7976931348623157e308", "1.7976931348623157e+308", nil},