go.net/ipv4: remove arguments from example functions
go.net/ipv4: remove arguments from example functions

The testing packege expects that Example functions in each
package don't take any arguments. Will do so for the safety.

R=iant, dave, minux.ma, adg
CC=golang-dev
https://golang.org/cl/6591076

subuk/net,chenzlabs/net,yangxianjun/net,cmars/tools,foreversmart/net,muzining/net,w4ngyi/net,kiip/net,albertjin/golang-net,gomini/net,kiip/net,cesanta/goxnet,dafyddcrosby/net,yangxianjun/net,veliamsli/net,flowlo/go-net,DramaFever/golang.org-x-net,gomini/net,raboof/net,cesanta/goxnet,raboof/net,cmars/tools,chenzlabs/net,foreversmart/net,mckinney-subgraph/net,flowlo/go-net,DramaFever/golang.org-x-net,dafyddcrosby/net,subuk/net,mckinney-subgraph/net,golang/net,muzining/net,zabawaba99/net,veliamsli/net,albertjin/golang-net,cmars/tools,zabawaba99/net,w4ngyi/net,cmars/tools