Migrated dialog_windows.go to use func() for uitask.

dialog_windows.go

@@ -30,21 +30,17 @@ func _msgBox(parent *Window, primarytext string, secondarytext string, uType uin
 	go func() {
 		ret := make(chan uiret)
 		defer close(ret)
-		uitask <- &uimsg{
-			call: _messageBox,
-			p: []uintptr{
+		uitask <- func() {
+			r1, _, err := _messageBox.Call(
 				uintptr(parenthwnd),
 				utf16ToArg(ptext),
 				utf16ToArg(ptitle),
-				uintptr(uType),
-			},
-			ret: ret,
+				uintptr(uType))
+			if r1 == 0 { // failure
+				panic(fmt.Sprintf("error displaying message box to user: %v\nstyle: 0x%08X\ntitle: %q\ntext:\n%s", err, uType, os.Args[0], text))
+			}
+			retchan <- int(r1)
 		}
-		r := <-ret
-		if r.ret == 0 { // failure
-			panic(fmt.Sprintf("error displaying message box to user: %v\nstyle: 0x%08X\ntitle: %q\ntext:\n%s", r.err, uType, os.Args[0], text))
-		}
-		retchan <- int(r.ret)
 	}()
 	return retchan
 }