os.Open doesn't exist in multi-argument form in recent versions of Go.

diff -x config.log -x config.status -ru tmp/autoconf-2.69/lib/autoconf/go.m4 work/autoconf-2.69/lib/autoconf/go.m4
--- tmp/autoconf-2.69/lib/autoconf/go.m4	2012-01-21 13:46:39.000000000 +0000
+++ work/autoconf-2.69/lib/autoconf/go.m4	2012-04-26 12:55:17.535998327 +0100
@@ -61,7 +61,7 @@
 # Produce source that performs I/O.
 m4_define([_AC_LANG_IO_PROGRAM(Go)],
 [AC_LANG_PROGRAM([import ( "fmt"; "os" )],
-[f, err := os.Open("conftest.out", os.O_CREATE|os.O_WRONLY, 0777)
+[f, err := os.Create("conftest.out")
  if err != nil {
 	fmt.Println(err)
 	os.Exit(1)
@@ -107,7 +107,7 @@
 	"os"
 )
 ],
-[f, err := os.Open("conftest.val", os.O_CREATE|os.O_WRONLY, 0777)
+[f, err := os.Create("conftest.val")
  if err != nil {
 	os.Exit(1)
  }