Added Mac OS X Textbox Go-side implementation. Doesn't quite work yet.

objc_darwin.h

@@ -79,7 +79,7 @@ extern id newLabel(void);
 extern id newGroup(id);
 extern const char *groupText(id);
 extern void groupSetText(id, char *);
-extern id newTextbox(id);
+extern id newTextbox(void);
 extern char *textboxText(id);
 extern void textboxSetText(id, char *);
 

textbox_darwin.go

@@ -0,0 +1,33 @@
+// 24 october 2014
+
+package ui
+
+import (
+	"unsafe"
+)
+
+// #include "objc_darwin.h"
+import "C"
+
+type textbox struct {
+	*scroller
+}
+
+func newTextbox() Textbox {
+	id := C.newTextbox()
+	t := &textbox{
+		scroller:		newScroller(id, true),		// border on Textbox (TODO confirm type)
+	}
+	// TODO preferred size
+	return t
+}
+
+func (t *textbox) Text() string {
+	return C.GoString(C.textboxText(t.id))
+}
+
+func (t *textbox) SetText(text string) {
+	ctext := C.CString(text)
+	defer C.free(unsafe.Pointer(ctext))
+	C.textboxSetText(t.id, ctext)
+}