add megacheck as makefile target (#9288)

Fix code issues in channel_test.go

Fix Channel Test Issues detected by Megacheck

Fix API Emoji Test Issues detected by Megacheck

Fixed API Issues Reported by Megacheck

Fixed App issues reported by megacheck

Remaining fixes

removed test added by mistake from old HEAD

gofmt

Store Fixes

simplified returns

Fix test for multi member channel delete

revert to delete unused function

plugin/interface_generator/main.go

@@ -229,7 +229,7 @@ func (g *hooksRPCClient) {{.Name}}{{funcStyle .Params}} {{funcStyle .Return}} {
 			g.log.Error("RPC call {{.Name}} to plugin failed.", mlog.Err(err))
 		}
 	}
-	return {{destruct "_returns." .Return}}
+	{{ if .Return }} return {{destruct "_returns." .Return}} {{ end }}
 }
 
 func (s *hooksRPCServer) {{.Name}}(args *{{.Name | obscure}}Args, returns *{{.Name | obscure}}Returns) error {
@@ -260,7 +260,7 @@ func (g *apiRPCClient) {{.Name}}{{funcStyle .Params}} {{funcStyle .Return}} {
 	if err := g.client.Call("Plugin.{{.Name}}", _args, _returns); err != nil {
 		log.Printf("RPC call to {{.Name}} API failed: %s", err.Error())
 	}
-	return {{destruct "_returns." .Return}}
+	{{ if .Return }} return {{destruct "_returns." .Return}} {{ end }}
 }
 
 func (s *apiRPCServer) {{.Name}}(args *{{.Name | obscure}}Args, returns *{{.Name | obscure}}Returns) error {