math: be consistent in how we document special cases

Change-Id: Ic6bc4af7bcc89b2881b2b9e7290aeb6fd54804e2
Reviewed-on: https://go-review.googlesource.com/2239Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/math/nextafter.go

@@ -5,7 +5,8 @@
 package math
 
 // Nextafter32 returns the next representable float32 value after x towards y.
-// Special cases:
+//
+// Special cases are:
 //	Nextafter32(x, x)   = x
 //	Nextafter32(NaN, y) = NaN
 //	Nextafter32(x, NaN) = NaN
@@ -26,7 +27,8 @@ func Nextafter32(x, y float32) (r float32) {
 }
 
 // Nextafter returns the next representable float64 value after x towards y.
-// Special cases:
+//
+// Special cases are:
 //	Nextafter64(x, x)   = x
 //	Nextafter64(NaN, y) = NaN
 //	Nextafter64(x, NaN) = NaN