exp/template: document that comments may span newlines.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/4855045

src/pkg/exp/template/doc.go

@@ -16,7 +16,7 @@ structure as execution proceeds.
 The input text for a template is UTF-8-encoded text in any format.
 "Actions"--data evaluations or control structures--are delimited by
 "{{" and "}}"; all text outside actions is copied to the output unchanged.
-Actions may not span newlines.
+Actions may not span newlines, although comments can.
 
 Once constructed, templates and template sets can be executed safely in
 parallel.
@@ -28,7 +28,8 @@ data, defined in detail below.
 
 */
 //	{{/* a comment */}}
-//		A comment; discarded. Comments do not nest.
+//		A comment; discarded. May contain newlines.
+//		Comments do not nest.
 /*
 
 	{{pipeline}}