syscall: fix solaris build

Solaris does not define syscall.{Mmap,Munmap}. Move the Mmap test to a new file and exclude solaris as discussed.

LGTM=aram
R=aram, mikioh.mikioh, iant
CC=golang-codereviews
https://golang.org/cl/68720043

src/pkg/syscall/mmap_unix_test.go

+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build darwin dragonfly freebsd linux netbsd openbsd
+
+package syscall_test
+
+import (
+	"syscall"
+	"testing"
+)
+
+func TestMmap(t *testing.T) {
+	b, err := syscall.Mmap(-1, 0, syscall.Getpagesize(), syscall.PROT_NONE, syscall.MAP_ANON|syscall.MAP_PRIVATE)
+	if err != nil {
+		t.Fatalf("Mmap: %v", err)
+	}
+	if err := syscall.Munmap(b); err != nil {
+		t.Fatalf("Munmap: %v", err)
+	}
+}

src/pkg/syscall/syscall_unix_test.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build freebsd dragonfly darwin linux netbsd openbsd solaris
+// +build darwin dragonfly freebsd linux netbsd openbsd solaris
 
 package syscall_test
 
@@ -77,16 +77,6 @@ func TestFcntlFlock(t *testing.T) {
 	}
 }
 
-func TestMmap(t *testing.T) {
-	b, err := syscall.Mmap(-1, 0, syscall.Getpagesize(), syscall.PROT_NONE, syscall.MAP_ANON|syscall.MAP_PRIVATE)
-	if err != nil {
-		t.Fatalf("Mmap: %v", err)
-	}
-	if err := syscall.Munmap(b); err != nil {
-		t.Fatalf("Munmap: %v", err)
-	}
-}
-
 // TestPassFD tests passing a file descriptor over a Unix socket.
 //
 // This test involved both a parent and child process. The parent