Add BSD support (openbsd, freebsd, solaris)

src/yggdrasil/tun_other.go

@@ -1,10 +1,13 @@
 // +build !linux
 // +build !darwin
 // +build !windows
+// +build !openbsd
+// +build !freebsd
+// +build !solaris
 
 package yggdrasil
 
-import water "github.com/songgao/water"
+import water "github.com/neilalexander/water"
 
 // This is to catch unsupported platforms
 // If your platform supports tun devices, you could try configuring it manually