swig -go: treat non-const references as pointers

Also clean up the handling of int* and int& to convert between the C
type int and the Go type int, which are often different sizes.

Fixes #2210

Examples/test-suite/go/go_director_inout_runme.go

@@ -14,6 +14,26 @@ func (p *GoMyClass) Adjust(m map[string]interface{}) wrap.GoRetStruct {
 	return wrap.GoRetStruct{s}
 }
 
+func (p *GoMyClass) S1(s string) {
+	if s != "S1" {
+		panic(s)
+	}
+}
+
+func (p *GoMyClass) S2(s *string) {
+	if *s != "S2" {
+		panic(s)
+	}
+	*s = "R2"
+}
+
+func (p *GoMyClass) S3(s *string) {
+	if *s != "S3" {
+		panic(s)
+	}
+	*s = "R3"
+}
+
 func main() {
 	a := wrap.NewDirectorMyClass(&GoMyClass{})
 	m := map[string]interface{}{
@@ -24,6 +44,18 @@ func main() {
 		panic(s)
 	}
 
+	a.S1("S1")
+	str := "S2"
+	a.S2(&str)
+	if str != "R2" {
+		panic(str)
+	}
+	str = "S3"
+	a.S3(&str)
+	if str != "R3" {
+		panic(str)
+	}
+
 	a = wrap.NewDirectorMyClass(nil)
 	s = a.Adjust(m)
 	if s.Str != `{"first":"second"}` {