[TIMOB-20008] iOS: Rename AlertDialog placeholder properties to hintText

   var win = Ti.UI.createWindow({  
     title: 'Click window to test',
     backgroundColor: 'white',
     exitOnClose: true,
     fullscreen: false
   });
   
   var placeholder = Titanium.UI.createButton({
      title: 'Plain placeholder',
      top: 10,
      left: 10,
      width: Ti.UI.SIZE,
      height: Ti.UI.SIZE
   });
   
   placeholder.addEventListener('click',function(e) {
       var dialog = Ti.UI.createAlertDialog({
       	message: 'Would you like to delete the file?',
       	title: 'Delete',
       	style: Titanium.UI.iOS.AlertDialogStyle.PLAIN_TEXT_INPUT,
       	placeholder:"The one"
     	});
     	dialog.show();
   });
   
   var loginPlaceholder = Titanium.UI.createButton({
      title: 'Full login placeholder',
      top: 10,
      left: 150,
      width: Ti.UI.SIZE,
      height: Ti.UI.SIZE
   });
   
   loginPlaceholder.addEventListener('click',function(e) {
       var dialog = Ti.UI.createAlertDialog({
       	buttonNames: ['Confirm', 'Cancel', 'Help'],
       	message: 'Would you like to delete the file?',
       	title: 'Delete',
       	style: Titanium.UI.iOS.AlertDialogStyle.LOGIN_AND_PASSWORD_INPUT,
       	loginPlaceholder:"The One",
       	passwordPlaceholder:"The Second"
     	});
     	dialog.show();
   });
   
   win.add(placeholder);
   win.add(loginPlaceholder);
   win.open();