fix: write header marking files as autogenerated

See GX-2234. This is the de-facto standard (see
golang/go#13560 (comment))
and tools like golint will ignore such files.

Author: guelfey

wsdlgo/encoder.go

@@ -223,7 +223,7 @@ func (ge *goEncoder) encode(w io.Writer, d *wsdl.Definitions) error {
 		}
 	}
 
-	fmt.Fprintf(w, "package %s\n\nimport (\n", ge.packageName)
+	fmt.Fprintf(w, "// Code generated by wsdl2go. DO NOT EDIT.\n\npackage %s\n\nimport (\n", ge.packageName)
 	for pkg := range ge.needsStdPkg {
 		fmt.Fprintf(w, "%q\n", pkg)
 	}