fix #751

add config ListenTCP4

when user want to listen on the TCP4, because now almost use the ipv4.
but default lister on the ipv6

filter.go

@@ -14,6 +14,11 @@
 
 package beego
 
+import "github.com/astaxie/beego/context"
+
+// FilterFunc defines filter function type.
+type FilterFunc func(*context.Context)
+
 // FilterRouter defines filter operation before controller handler execution.
 // it can match patterned url and do filter function when action arrives.
 type FilterRouter struct {