cmd/goyacc: append trailing newline to text "Code generated by goyacc"

Fixes golang/go#26478

Change-Id: Ieaf7dcaf639b277555580964acfff034393284e2
GitHub-Last-Rev: f2a6ab2a51
GitHub-Pull-Request: golang/tools#39
Reviewed-on: https://go-review.googlesource.com/124995
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

cmd/goyacc/yacc.go

@@ -387,7 +387,7 @@ func setup() {
 	yaccpar = strings.Replace(yaccpartext, "$$", prefix, -1)
 	openup()
 
-	fmt.Fprintf(ftable, "// Code generated by goyacc %s. DO NOT EDIT.", strings.Join(os.Args[1:], " "))
+	fmt.Fprintf(ftable, "// Code generated by goyacc %s. DO NOT EDIT.\n", strings.Join(os.Args[1:], " "))
 
 	defin(0, "$end")
 	extval = PRIVATE // tokens start in unicode 'private use'