test: don't use package main for files without a main function

Part of issue 2833, but works fine with current test runner.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/5606056
diff --git a/test/eof1.go b/test/eof1.go
index c39a3cf..060c902 100644
--- a/test/eof1.go
+++ b/test/eof1.go
@@ -4,6 +4,6 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-package main
+package eof1
 
 // No newline at the end of this comment.
\ No newline at end of file